Made available in DSpace on 2017-07-21T14:35:55Z (GMT). No. of bitstreams: 1 Jessica Fontoura.pdf: 1793344 bytes, checksum: 7d26d97100cdf210c653767cf8a12d40 (MD5) Previous issue date: 2016-02-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease. Depression and anxiety are common psychological disorders in patients suffering from PD. In the literature, there is much discussion about the probable mechanism leading to depression in PD and if it is associated with other psychiatric symptoms such as anxiety. It is still unclear which neurotransmitters and which neural pathways alterations could be related to the development of these non-motor symptoms. This study aimed to test how distinct monoamine neurotransmitters reuptake inhibitors interfere in the behavioral changes caused by damage to the nigrostriatal pathway with 6-OHDA in rats. To test this hypothesis, animals were subjected to stereotaxic surgery for infusion of 6-OHDA into their medial forebrain bundle (MFB) or their substantia nigra compacta (SN). These animals were divided in groups, one receiving bupropion (dopamine uptake blocker), fluoxetine (serotonin uptake blocker) or nortriptylin (noradrenalin uptake blocker), apart from a 6-OHDA with no blockers and a control group, which received 0,9% saline solution instead of 6-OHDA. At day 21 after surgery, behavioral testing started. Locomotor activity was evaluated by the open field test; depressive-like behavior by the forced swimming and the sucrose preference tests; and anxious behavior by the elevated plus maze test. The results were analyzed by one-way ANOVA, followed by post hoc Newman-Keuls post hoc test. The injury provoked by the infusion of the toxin in the SN was able to cause non-motor symptoms of PD, such as depression and anxiety, with no presentation of motor impairment by the animals, while injury in the FPM didn’t cause the same symptoms. On the SN lesioned animals, the administration of nortryptiline and bupropion were able to prevent from the 6-OHDA effect on the time spent on the open arm of the elevated plus maze test. On the same animals, bupropion, nortriptyline and fluoxetine were capable of prevent the reduction of the number of entrances to the center and the open arms of the same maze, and the reduction of swimming time and increase of immobility time caused by 6-OHDA on the forced swimming test. These data indicate that the SN lesion causes more behavior alteration than the MFB lesion in rats, also demonstrating that these motor alterations depend on the effect of the toxin on dopaminergic, noradrenergic and serotoninergic neurons. This contributes to the characterization of this model of behavioral alterations related to the nigrostriatal lesion. / A doença de Parkinson (DP) é a segunda doença neurodegenerativa mais frequente relacionada à idade. A depressão e a ansiedade são distúrbios psicológicos comuns em pacientes acometidos pela DP. Na literatura, muito se discute sobre o provável mecanismo que leva a depressão na DP e se está relacionada a outros sintomas psiquiátricos, como ansiedade. Ainda não está claro quais neurotransmissores ou quais vias neurais estão alteradas no desenvolvimento desses sintomas não-motores. Este estudo teve como objetivo testar como o bloqueio de recaptadores de neurotransmissores monoaminérgicos interfere nas alterações comportamentais provocadas pela lesão da via nigroestriatal com 6-OHDA em ratos. Para testar esta hipótese, os animais foram submetidos a cirurgia estereotáxica para infusão de 6-OHDA no feixe prosencefálico medial (FPM) ou na substância negra (SN). Estes animais foram divididos em grupos, sendo que um recebeu bupropiona (inibidor da recaptação de dopamina), fluoxetina (inibidor da recaptação de serotonina) ou nortriptilina (inibidor da recaptação de noradrenalina), além de um grupo sem inibidores e outro controle, com infusão de salina 0,9% no lugar da 6-OHDA. No 21º dia após a cirurgia, os testes comportamentais tiveram início. A atividade locomotora foi avaliada através do teste de campo aberto e o comportamento tipo depressivo e de ansiedade pelos testes da natação forçada, preferência à sacarose e labirinto em cruz elevado. Os resultados foram analisados por ANOVA de uma via seguida de teste post hoc Newman-Keuls. A lesão pela infusão da toxina na SN foi capaz de causar sintomas não-motores da DP, como depressão e ansiedade, sem que houvesse apresentação de prejuízo motor pelos animais, enquanto que a lesão no FPM não causou os mesmos sintomas. Nos animais lesados na SN, a administração de nortriptilina e a de bupropiona foram capazes de reverter o efeito da 6-OHDA no tempo de permanência no braço aberto do labirinto em cruz. Nesses mesmos animais, a bupropiona, a nortriptilina e a fluoxetina foram capazes de reverter os comportamentos de número de entradas no centro e no braço aberto desse labirinto, assim como de evitar a redução do tempo de natação e o aumento do tempo de imobilidade na natação forçada, também causados pela lesão com 6-OHDA. Esses dados indicam que a lesão na SN provoca mais alterações do que a do FPM em ratos, além de demonstrar que essas alterações dependem de efeitos dessa toxina em neurônios dopaminérgicos, noradrenérgicos e serotoninérgicos. Isto então contribui para a caracterização do modelo de alterações comportamentais ligados à lesão nigroestriatal.

La mélatonine est une neuro-hormone secrétée par la glande pinéale pour réguler les rythmes circadiens, le sommeil, la physiologie de la rétine, la reproduction saisonnière et diverses fonctions neuronales. La mélatonine exerce ses fonctions en se liant à deux récepteurs membranaires appelés MT1 et MT2 qui appartiennent à la famille des récepteurs couplés aux protéines G (RCPG). Les RCPG sont connus pour former des homo- et hétérodimères mais la pertinence physiologique de ces complexes reste à démontrer. Plusieurs études montrent que la fonction de ces complexes ne se limite pas à la régulation des protéines G hétérotrimériques, mais inclue également la régulation d'autres protéines comme les transporteurs et les canaux ioniques. Dans ce travail, nous rapportons la formation d'hétérodimères MT1/MT2 dans les photorécepteurs de la rétine de souris et nous montrons que l’augmentation de la sensibilité de ces cellules à la lumière par la mélatonine requiert l'activation de la voie Gq/PLC/PKC qui est spécifique de l’hétéromère. Cette étude confirme alors la pertinence physiologique de l’hétérodimérisation des récepteurs de la mélatonine.Nous avons ensuite cherché à identifier de nouveaux partenaires de MT1 et MT2 en effectuant plusieurs cribles protéomiques et génétiques et un interactome de 378 protéines a pu être construit. L'analyse bioinformatique a révélé la présence de plusieurs protéines présynaptiques (canaux calciques voltage-dépendants Cav2.2, SNAP25, Synapsin et Munc-18) dans l'interactome MT1. Parmi ces partenaires, nous avons montré dans les cellules CHO que le récepteur MT1 interagit avec la protéine Cav2.2 et inhibe l’entrée du calcium d'une manière indépendante de la stimulation par l’agoniste, ce qui suggère un rôle régulateur de MT1 dans la libération des neurotransmetteurs.Un autre partenaire caractérisé est le transporteur de la dopamine DAT. L'interaction physique de DAT avec les récepteurs de la mélatonine diminue l’expression de DAT à la surface cellulaire et diminue l'absorption de la dopamine dans les cellules HEK293. La pertinence physiologique de ces observations a été appuyée par l’augmentation de la recapture de la dopamine dans les synaptosomes du striatum de souris knock-out pour les récepteurs de la mélatonine. En conclusion, ce rapport montre que la construction des interactomes des RCPG offre de nouvelles perspectives pour la découverte de nouvelles fonctions de ces récepteurs, comme les fonctions rétiniennes et neuronales des récepteurs de la mélatonine dans notre étude. La formation de complexes RCPG/RCPG, RCPG/canaux ioniques et RCPG/transporteurs peut avoir un effet fonctionnel réciproque au niveau de l’activité du récepteur et de ces partenaires, mettant ainsi en évidence de nouveaux mécanismes moléculaires de cross-talk cellulaire. / Melatonin is a neurohormone secreated by the pineal gland in a circadian manner. This hormone is involved in the regulation of circadian rhythms, sleep, retinal physiology, seasonal reproduction and various neuronal functions. Melatonin exerts its effects through two G protein-coupled receptors (GPCR) called MT1 and MT2. GPCRs are known to form homo- and heterodimers, but the physiological relevance of these complexes remains a matter of debate. An increasing number of reports show that the function of these GPCR complexes is not restricted to the regulation of heterotrimeric G proteins but include also the regulation of other proteins like transporters and ion channels. Here, we report the formation of MT1/MT2 heterodimers in mouse retinal rod photoreceptors and show that the enhancing effect of melatonin on light sensitivity in these cells requires the activation of the heteromer-specific Gq/PLC/PKC signaling pathway. This study demonstrates the physiological relevance of GPCR heterodimerization.We next searched for new MT1 and MT2 interacting proteins in an unbiased manner by performing several proteomic and genetic screens. An interactome of 378 proteins was built. Bioinformatic analysis revealed the presence of several presynaptic proteins (voltage-gated calcium channel Cav2.2, SNAP25, Synapsin and Munc-18) in the MT1 interactome. Presynaptic localization of MT1 and spatial proximity with presynaptic proteins was confirmed in mouse and rat brains. Among these potential partners, we show that MT1 physically interacts with Cav2.2 in CHO cell line and inhibits Cav2.2-promoted Ca2+ entry in an agonist-independent manner suggesting a regulatory role of MT1 in neurotransmitter release.Another proteins identified in the screens was the dopamine transporter DAT. Physical interaction of DAT with melatonin receptors decreased DAT cell surface expression and diminished dopamine uptake in HEK293 cell. Supporting this result we found using the in vivo model of melatonin receptors knockout mice a respective increase of dopamine uptake in synaptosomal preparations of the striatum of supporting the physiological relevance of these GPCR/transporter complexes. In conclusion, this report shows that GPCR interactome building provides new insights into receptor function, like retinal and neuronal functions of melatonin receptors in our case. Formation of GPCR/GPCR, GPCR/ion channel and GPCR/transporter complexes may have a reciprocal functional impact, on the activity of the receptor and interacting partners thus elucidating new molecular mechanisms cellular cross-talk.

Tingan Chen. / "March 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 100-142). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

帕金森病（PD）是一種常見的神經退行性疾病，其特徵性的癥狀是運動功能減弱，常伴有認知障礙如工作記憶缺陷。大多數癥狀源於中腦多巴胺神經元的進行性缺失。目前的治療常隨時間進展誘發嚴重的副反應，促使我們進一步研究PD的病理生理學機制。一般認為基底神經節直接和間接通路不平衡的活動導致PD的運動缺陷，但目前關於基底神經節環路突觸特性改變的研究還很少。對PD認知障礙機制的研究則更為少見。 / 本研究中，我們首先關注在對基底神經節提供主要輸入的皮質紋狀體通路。應用全細胞膜片鉗技術結合皮質刺激，并利用在D2受體表達神經元表達綠色螢光蛋白的轉基因小鼠，我們發現PD狀態下，在間接通路表達D2受體的中型多棘神經元（D2 MSN）上記到的皮質紋狀體通路AMPA受體介導電流的成對脉沖比值（PPR）以及NMDA受體介導電流的PPR均降低。此外皮質至D2 MSN突觸間隙的谷氨酸水平也增加而不伴有谷氨酸轉運體的功能異常。這些結果證明PD狀態下皮質至間接通路D2 MSN的谷氨酸釋放選擇性增加。結合基底神經節的功能環路考慮，至間接通路紋狀體投射神經元的皮質谷氨酸釋放增加可能參與了PD的運動癥狀。 / 我們接下來研究了皮質-D2 MSN通路的下游環節即紋狀體至蒼白球通路傳遞的改變。在蒼白球（GP）神經元上應用全細胞膜片鉗記錄結合紋狀體刺激，我們發現在6-羥多巴損毀之後，紋狀體蒼白球通路的PPR降低，GP神經元記到的紋狀體刺激誘發的抑制性突觸后電流（eIPSC）的變異係數降低,以及GP神經元記到的微型IPSC的頻率增加，這些結果證明紋狀體至蒼白球的GABA釋放增加。突觸前III型代謝型谷氨酸受體介導的對紋狀體蒼白球傳遞的抑制作用消失導致了紋狀體蒼白球通路GABA釋放的增加。這一增加，通過影響間接通路的下游環節，也可能參與了PD的運動癥狀。 / 為探討認知障礙的機制，我們研究了參與工作記憶功能的邊緣前皮質至伏核（NAc）的投射。應用與第一部份相似的研究方法，我們發現多巴胺受體對邊緣前皮質NAc通路的傳遞存在高度精確和補償性的調節。在邊緣前皮質-NAc D1 MSN通路，D1和D2受體突觸前分別介導對該傳遞的抑制性和易化性調節。然而，在D2 MSN相關的邊緣前皮質-NAc通路，上述作用發生了反轉。在耗竭NAc多巴胺之後，D2 MSN上誘發到的興奮性突觸后電流增加，提示邊緣前皮質-NAc D2 MSN傳遞增加。此外，在多巴胺損毀的情況下，激活D1和D2受體不再調節邊緣前皮質NAc通路的傳遞。結合邊緣環路考慮，邊緣前皮質至D2 MSN的谷氨酸釋放增加可能參與了PD的認知障礙。 / 綜上所述，PD狀態下，繼多巴胺缺失之後，多條通路發生可塑性改變，這些改變可能參與PD的運動和認知癥狀。 / Parkinson’s disease (PD) is a common neurodegenerative disease with characteristic hypokinetic motor symptoms and cognitive impairments like working memory deficits. Most of the symptoms are derived from progressive loss of dopaminergic neurons in the midbrain. Current therapies often induce severe side effects with time, which promotes us to further investigate the pathophysiological mechanism of PD. It is generally thought that the imbalanced activity between direct and indirect pathways of the basal ganglia underlies the motor deficits in PD, but little is studied about the changes in synaptic properties of the sub-circuits. Even less is known about the mechanism responsible for the cognitive dysfunctions in PD. / In our study, we first focused on the corticostriatal pathway that provides a major input to the basal ganglia. Employing whole-cell patch-clamp recordings with cortical stimulation as well as by taking advantage of transgenic mice with green fluorescent protein co-expressed in the D2 receptor-expressing neurons, we found a selective increase in cortical glutamate release onto indirect-pathway D2 receptor-expressing medium-sized spiny neurons (D2 MSNs), as indicated by reduced corticostriatal AMPA paired-pulse ratios (PPRs) and NMDA PPRs in D2 MSNs as well as increased glutamate level in cortex-D2 MSN synaptic cleft without malfunction in glutamate transporters in parkinsonian states. Considering from the functional organization of the basal ganglia circuits, the increased corticostriatal glutamate release onto indirect-pathway striatal projection neurons may contribute to the motor symptoms of PD. / We next studied whether the striatopallidal transmission, downstream to the cortex-D2 MSNs pathway, is also altered in parkinsonian states. Combining whole-cell patch-clamp recordings in globus pallidus (GP) neurons with striatal stimulation, we demonstrated that the striatopallidal GABA release was increased following 6-hydroxydopamine lesion, as indicated by decreased striatopallidal PPRs, reduced coefficient of variation of striatally evoked inhibitory postsynaptic currents (eIPSCs) and elevated frequency of miniature IPSCs in GP neurons. The loss of tonic presynaptic group III metabotropic glutamate receptors-mediated inhibition on striatopallidal transmission accounted for the increased striatopallidal GABA release. The increase in the striatopallidal GABA release, through affecting the downstream of the indirect pathway, would also contribute to the motor symptoms in PD. / To investigate the underlying mechanism of cognitive deficits, we targeted the prelimbic cortex-nucleus accumbens (NAc) projection that is critical for working memory function. Using similar approaches as the first part, we observed highly precise and complementary modulations by dopamine receptors, with D1 and D2 receptors presynaptically mediating the inhibition and facilitation of the prelimbic cortex-NAc D1 MSN transmission, respectively, and reversed effects in D2 MSN-associated pathway. Following dopamine depletion in NAc, an enhanced prelimbic cortex-NAc D2 MSN transmission was indicated by selectively increased excitatory postsynaptic current evoked in D2 MSNs. Moreover, in the dopamine-depleted state, activating D1 and D2 receptors failed to modulate the prelimbic cortex-NAc transmission. Considering from the information flow in the limbic loop, the increased prelimbic cortical glutamate release onto D2 MSNs may contribute to the cognitive impairments in PD. / In conclusion, in the parkinsonian states, multiple pathways undergo plasticity changes subsequent to dopamine depletion, which may underlie the motor and cognitive symptoms in PD. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Cui, Qiaoling. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 160-191). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chapter Chapter 1 --- General introduction --- p.1 / Chapter 1.1 --- Parkinson’s disease --- p.1 / Chapter 1.1.1 --- Symptoms --- p.1 / Chapter 1.1.2 --- Etiology --- p.1 / Chapter 1.1.3 --- Pathology and pathophysiology --- p.2 / Chapter 1.1.4 --- Therapy --- p.5 / Chapter 1.1.4.1 --- L-DOPA and dopamine receptor agonists treatments --- p.5 / Chapter 1.1.4.2 --- Deep brain stimulation (DBS) and lesional surgery treatments --- p.6 / Chapter 1.1.4.3 --- Neural transplantation --- p.7 / Chapter 1.1.4.4 --- Treatment of nonmotor symptoms --- p.8 / Chapter 1.2 --- Basal ganglia --- p.8 / Chapter 1.2.1 --- Components of basal ganglia --- p.8 / Chapter 1.2.2 --- Pathways in basal ganglia --- p.8 / Chapter 1.2.2.1 --- Anatomical organization of the basal ganglia pathways --- p.8 / Chapter 1.2.2.2 --- Functional consequences of the basal ganglia pathways --- p.10 / Chapter 1.3 --- Striatum --- p.11 / Chapter 1.3.1 --- Anatomy of the striatum --- p.11 / Chapter 1.3.1.1 --- Cellular heterogeneity in the striatum --- p.12 / Chapter 1.3.1.1.1 --- MSNs --- p.12 / Chapter 1.3.1.1.1.1 --- Subpopulations --- p.13 / Chapter 1.3.1.1.1.2 --- Morphology --- p.13 / Chapter 1.3.1.1.1.3 --- Electrophysiological properties --- p.14 / Chapter 1.3.1.1.2 --- Cholinergic interneurons --- p.15 / Chapter 1.3.1.1.3 --- GABAergic interneurons --- p.17 / Chapter 1.3.1.2 --- Innervation of the striatum --- p.18 / Chapter 1.3.1.3 --- Output of the striatum --- p.21 / Chapter 1.3.2 --- Function of the striatum --- p.21 / Chapter 1.3.2.1 --- Function of the associative striatum --- p.22 / Chapter 1.3.2.2 --- Function of the sensorimotor striatum --- p.22 / Chapter 1.3.3 --- The corticostriatal system --- p.23 / Chapter 1.3.3.1 --- Anatomy of the corticostriatal system --- p.24 / Chapter 1.3.3.2 --- Physiology of the corticostriatal system --- p.25 / Chapter 1.3.3.3 --- Function of the corticostriatal system --- p.26 / Chapter 1.3.4 --- Striatum, corticostriatal system and PD --- p.26 / Chapter 1.4 --- GPe --- p.29 / Chapter 1.4.1 --- Anatomy of GPe --- p.29 / Chapter 1.4.1.1 --- Cellular heterogeneity in GPe --- p.29 / Chapter 1.4.1.2 --- Innervation of GPe --- p.31 / Chapter 1.4.1.3 --- Output of GPe --- p.33 / Chapter 1.4.2 --- Neurotransmission in GPe --- p.34 / Chapter 1.4.2.1 --- GABAA receptors in GPe --- p.34 / Chapter 1.4.2.2 --- GABAB receptors in GPe --- p.35 / Chapter 1.4.2.3 --- Evoked responses in GPe from direct striatal and pallidal stimulations --- p.37 / Chapter 1.4.3 --- GPe, striatopallidal system and PD --- p.38 / Chapter 1.5 --- NAc --- p.40 / Chapter 1.5.1 --- Anatomy of NAc --- p.40 / Chapter 1.5.1.1 --- Subregions --- p.40 / Chapter 1.5.1.2 --- Cell heterogeneity in NAc --- p.42 / Chapter 1.5.1.2.1 --- MSNs --- p.42 / Chapter 1.5.1.2.2 --- Interneurons --- p.42 / Chapter 1.5.1.3 --- Inervation of NAc --- p.43 / Chapter 1.5.1.4 --- Output of NAc --- p.43 / Chapter 1.5.2 --- Function of NAc --- p.43 / Chapter 1.5.3 --- The prefrontal cortex (PFC)-NAc system --- p.43 / Chapter 1.5.4 --- NAc, PFC-NAc system and PD --- p.44 / Chapter 1.6 --- Objectives --- p.45 / Chapter Chapter 2 --- General methods --- p.51 / Chapter 2.1 --- Electrophysiological experiments --- p.51 / Chapter 2.1.1 --- Slice preparation --- p.51 / Chapter 2.1.2 --- Whole-cell patch-clamp recordings --- p.52 / Chapter 2.1.3 --- Uncaging experiment --- p.54 / Chapter 2.1.4 --- Data analysis and statistics --- p.54 / Chapter 2.2 --- Dopamine depletion --- p.55 / Chapter 2.2.1 --- 6-hydroxydopamine (6-OHDA) injection into medial forebrain bundle (MFB) --- p.55 / Chapter 2.2.2 --- 6-OHDA injection into NAc --- p.56 / Chapter 2.2.3 --- Reserpine treatment --- p.56 / Chapter 2.3 --- Limb-use asymmetry test (cylinder test) --- p.57 / Chapter 2.4 --- Tyrosine hydroxylase (TH) immunohistochemistry and analysis --- p.57 / Chapter 2.4.1 --- TH immunohistochemistry of SNc and striatal slices --- p.57 / Chapter 2.4.2 --- TH immunohistochemistry and analysis of NAc slices --- p.58 / Chapter 2.5 --- Tracing study --- p.59 / Chapter 2.6 --- Genotyping and quantitative polymerase chain reaction (qPCR) --- p.60 / Chapter Chapter 3 --- Alteration of corticostriatal glutamatergic transmission onto D2 MSNs in PD models --- p.62 / Chapter 3.1 --- Summary --- p.62 / Chapter 3.2 --- Introduction --- p.63 / Chapter 3.3 --- Materials --- p.65 / Chapter 3.3.1 --- Animals --- p.65 / Chapter 3.3.2 --- Chemicals --- p.66 / Chapter 3.4 --- Results --- p.66 / Chapter 3.4.1 --- Comparison of corticostriatal paired-pulse ratios (PPRs) between hemizygotes and homozygotes of D2-EGFP BAC transgenic mice --- p.66 / Chapter 3.4.2 --- Corticostriatal AMPA PPR was specifically decreased in D2 MSNs following dopamine depletion --- p.67 / Chapter 3.4.2.1 --- Corticostriatal AMPA PPR was specifically decreased in D2 MSNs following reserpine treatment --- p.67 / Chapter 3.4.2.2 --- Corticostriatal AMPA PPR was specifically decreased in D2 MSNs following 6-OHDA lesion --- p.68 / Chapter 3.4.3 --- Increased glutamate release underlying reduction of corticostriatal PPR in D2 MSNs in parkinsonian states --- p.69 / Chapter 3.4.3.1 --- Effect of γ-DGG on the corticostriatal eEPSCs of D2 MSNs --- p.70 / Chapter 3.4.3.2 --- Effect of γ-DGG on the corticostriatal eEPSCs of D2 MSNs in the presence of CTZ --- p.70 / Chapter 3.4.3.3 --- Decay kinetics of eEPSCs of D2 MSNs in the presence of CTZ or PEPA were not consistently altered following dopamine depletion --- p.71 / Chapter 3.4.3.4 --- Corticostriatal NMDA PPR was decreased in D2 MSNs following dopamine depletion --- p.72 / Chapter 3.4.4 --- AMPA receptor occupancy was increased in D2 MSNs following dopamine depletion --- p.73 / Chapter 3.4.5 --- Increased postsynaptic AMPA receptor desensitization contributing to the reduction of corticostriatal PPR in D2 MSNs of parkinsonian states --- p.74 / Chapter 3.4.5.1 --- Effect of CTZ on the corticostriatal AMPA PPR of D2 MSNs --- p.74 / Chapter 3.4.5.2 --- Effect of PEPA on the corticostriatal AMPA PPR of D2 MSNs --- p.75 / Chapter 3.4.6 --- Loss of dopamine D2 receptor activation did not contribute to the increased corticostriatal glutamate release onto D2 MSNs in the parkinsonian states --- p.75 / Chapter 3.4.7 --- Postsynaptic Ca2+ involved in the modification of the corticostriatal transmission in D2 MSNs of parkinsonian state --- p.77 / Chapter 3.5 --- Discussion --- p.78 / Chapter 3.5.1 --- Corticostriatal glutamate release onto D2 MSNs was increased in the parkinsonian states --- p.78 / Chapter 3.5.2 --- AMPA receptor occupancy was increased in D2 MSNs following dopamine depletion --- p.80 / Chapter 3.5.3 --- Postsynaptic AMPA receptor desensitization was increased in D2 MSNs following dopamine depletion --- p.81 / Chapter 3.5.4 --- Loss of dopamine D2 receptor activation did not contribute to the increased corticostriatal glutamate release onto D2 MSNs in the parkinsonian states --- p.81 / Chapter 3.5.5 --- Postsynaptic Ca2+ involved in the modification of the corticostriatal transmission in D2 MSNs of parkinsonian state --- p.82 / Chapter 3.5.6 --- The increased corticostriatal glutamate release onto D2 MSNs and PD --- p.83 / Chapter Chapter 4 --- Alteration of striatopallidal GABAergic transmission in 6-OHDA lesioned PD model --- p.98 / Chapter 4.1 --- Summary --- p.98 / Chapter 4.2 --- Introduction --- p.99 / Chapter 4.3 --- Materials --- p.101 / Chapter 4.3.1 --- Animals --- p.101 / Chapter 4.3.2 --- Chemicals --- p.101 / Chapter 4.4 --- Results --- p.101 / Chapter 4.4.1 --- Striatopallidal paired-pulse ratio (PPR) was decreased following 6-OHDA lesion --- p.101 / Chapter 4.4.1.1 --- Striatopallidal PPR was unchanged following reserpine treatment --- p.102 / Chapter 4.4.1.2 --- Striatopallidal PPR was decreased following 6-OHDA lesion --- p.102 / Chapter 4.4.2 --- Increased striatopallidal GABA release underlying the reduction of striatopallidal PPR following 6-OHDA lesion --- p.103 / Chapter 4.4.2.1 --- CV of eIPSC1 in GP neurons was reduced following 6-OHDA lesion --- p.103 / Chapter 4.4.2.2 --- mIPSCs frequency was increased in GP neurons following 6-OHDA lesion --- p.104 / Chapter 4.4.3 --- Mechanism for the increased striatopallidal GABA release following 6-OHDA lesion --- p.105 / Chapter 4.4.3.1 --- Loss of dopamine D2 receptor activation did not contribute to the increased striatopallidal GABA release following 6-OHDA lesion --- p.105 / Chapter 4.4.3.2 --- GABAB receptor modulation did not contribute to the increased striatopallidal GABA release following 6-OHDA lesion --- p.106 / Chapter 4.4.3.3 --- Loss of presynaptic tonic group III mGluR inhibition accounted for the increased striatopallidal GABA release following 6-OHDA lesion --- p.107 / Chapter 4.5 --- Discussion --- p.109 / Chapter 4.5.1 --- Striatopallidal GABA release was increased in the parkinsonian state --- p.109 / Chapter 4.5.2 --- Mechanism underlying the increased striatopallidal GABA release in the parkinsonian state --- p.111 / Chapter 4.5.2.1 --- Loss of dopamine D2 receptor activation did not contribute to the increased striatopallidal GABA release following 6-OHDA lesion --- p.111 / Chapter 4.5.2.2 --- GABAB receptor modulation did not contribute to the increased striatopallidal GABA release following 6-OHDA lesion --- p.112 / Chapter 4.5.2.3 --- Loss of presynaptic tonic group III mGluR inhibition accounted for the increased striatopallidal GABA release following 6-OHDA lesion --- p.113 / Chapter 4.5.3 --- The increased striatopallidal GABA release and PD --- p.114 / Chapter 4.5.4 --- The striatopallidal group III mGluR system and PD --- p.116 / Chapter Chapter 5 --- Role of D1 and D2 receptors in prelimbic cortex-nucleus acumbens transmission in normal and parkinsonian states --- p.128 / Chapter 5.1 --- Summary --- p.128 / Chapter 5.2 --- Introduction --- p.129 / Chapter 5.3 --- Materials --- p.131 / Chapter 5.3.1 --- Animals --- p.131 / Chapter 5.3.2 --- Chemicals --- p.131 / Chapter 5.4 --- Results --- p.132 / Chapter 5.4.1 --- Prelimbic cortex innervated both D1 MSNs and D2 MSNs in core subregion of NAc- --- p.132 / Chapter 5.4.2 --- D1 and D2 receptors presynaptically modulated the D1 MSN-associated prelimbic cortex-NAc transmission in opposite manner --- p.133 / Chapter 5.4.3 --- D1 and D2 receptors presynaptically modulated the D2 MSN-associated prelimbic cortex-NAc transmission in a reverse manner --- p.134 / Chapter 5.4.4 --- Effects of D1 and D2 receptor antagonists on the prelimbic cortex-Nac transmission --- p.135 / Chapter 5.4.5 --- Basal synaptic transmission was enhanced in D2 MSN-associated prelimbic cortex-NAc pathway following NAc dopamine depletion --- p.136 / Chapter 5.4.6 --- D1 and D2 receptor modulation of the prelimbic cortex-NAc transmission disappeared following dopamine depletion --- p.137 / Chapter 5.5 --- Discussion --- p.138 / Chapter 5.5.1 --- Prelimbic cortex innervated both D1 MSNs and D2 MSNs in core subregion of NAc- --- p.138 / Chapter 5.5.2 --- Prelimbic cortex-NAc projections were presynaptically modulated by D1 and D2 receptors in a highly precise and complementary pattern --- p.138 / Chapter 5.5.3 --- Glutamatergic transmission was selectively enhanced in D2 MSN-associated prelimbic cortex-NAc pathway following NAc dopamine depletion --- p.140 / Chapter 5.5.4 --- D1 and D2 receptor modulation of the prelimbic cortex-NAc transmission was lost following dopamine depletion --- p.142 / Chapter Chapter 6 --- General discussion --- p.154 / Chapter 6.1 --- Enhanced corticostriatal glutamate release, enhanced striatopallidal GABA release and motor deficits in PD --- p.154 / Chapter 6.2 --- Enhanced prelimbic cortical glutamate release onto accumbal D2 MSNs and cognitive deficits in PD --- p.155 / Abbreviations --- p.158 / References --- p.160

O envelhecimento é um processo acompanhado por uma série de mudanças físicas, fisiológicas e psicológicas, além de ser caracterizado pelo declínio de diferentes funções motoras e cognitivas, que afetam a independência do idoso. Particularmente na mulher, um acompanhante inevitável do envelhecimento é a menopausa. Desse modo, é natural o interesse em medidas terapêuticas que possam ser utilizadas para minimizar os sintomas da menopausa, bem como o prejuízo motor e cognitivo. Assim, o presente estudo teve como objetivo (i) avaliar o efeito da idade nos aspectos comportamentais, neuroquímicos e de ácidos graxos poli-insaturados em ratas jovens (3 meses de idade), de meia-idade (12 meses de idade) e senescentes (18 meses de idade); e, (ii) avaliar os efeitos da administração prolongada (90 dias) de diferentes doses (50, 100 e 200 mg/kg/dia) de isoflavonas (ISOs) no perfil comportamental, na análise bioquímica sérica e de estradiol, na quantificação dos níveis de neurotransmissores encefálicos e achados anatomopatológicos em ratas de meia-idade. Os resultados da primeira etapa mostraram que: ratas com 12 e 18 meses de idade apresentaram: 1) diminuição da frequência de levantar e de grooming no campo aberto; 2) aumento do comportamento tipo-ansioso no labirinto em cruz elevado e na caixa claro-escuro; 3) prejuízo na memória espacial observada no labirinto de Barnes; 4) diminuição, sobretudo, nos níveis de dopamina e de seus metabólitos no córtex pré-frontal (CPF), no hipotálamo, no hipocampo e no estriado; 5) diminuição dos níveis dos hidróxidos 12 e 15/14 do ácido araquidônico (AA) no CPF de ratas com 18 meses de idade. Esses dados em conjunto evidenciam prejuízo motor e cognitivo, aumento do comportamento tipo-ansioso, bem como redução nos níveis de monoaminas e dos hidróxidos do AA com o avanço da idade das ratas. Em relação ao tratamento prolongado com diferentes doses de ISOs em ratas de meia-idade, os resultados mostraram que: 1) não houve alterações motoras e no comportamento tipo-ansioso; 2) evidenciou melhora no desempenho cognitivo espacial; 3) mostrou aumento nos níveis séricos de estradiol e 4) promoveu aumento nos níveis de glutamato e de GABA no CPF e no hipotálamo. Esses achados sugerem que o tratamento prolongado com diferentes doses de ISOs em ratas de meia-idade, foi capaz de melhorar a performance cognitiva espacial e esse efeito pode ser associado ao aumento dos níveis de estrógeno, bem como ao aumento dos níveis de glutamato e de GABA no córtex pré-frontal e no hipotálamo, evidenciando também um possível efeito neuroprotetor das ISOs em ambas regiões. / Aging is a process accompanied by a series of physical, physiological and psychological changes, besides being characterized by the decline of different motor and cognitive functions, which affect the independence of the elderly. Specifically, in women, an inevitable companion of aging is menopause. Therefore, it is of high interest therapeutic procedures that can be used to reduce the symptoms of menopause, as well as motor and cognitive impairment. Thus, the present study aimed to (i) evaluate the effect of age on behavioral, neurochemical and polyunsaturated fatty acids aspects in young (3 months old), middle-aged (12 months old) and senescent (18 months of age) female rats; and (ii) to evaluate the effects of prolonged (90 days) administration of different doses (50, 100 and 200 mg/kg/day) of isoflavones (ISOs) in the behavioral profile, biochemical and estradiol serum analysis, brain neurotransmitters levels and anatomopathological findings in middle-aged rats. Our first results showed that rats at 12 and 18 months of age: 1) presented a decrease in rearing and grooming frequency in the open field; 2) increase of anxiety-like behavior in the elevated plus maze and light-dark box; 3) spatial memory impairment observed in the Barnes maze; 4) a decrease mainly in the levels of dopamine and its metabolites in the prefrontal cortex (PFC), hypothalamus, hippocampus and striatum; 5) decreased levels of 12 and 15/14 arachidonic acid (AA) hydroxides in the PFC in 18-month old rats . These data altogether show motor and cognitive impairment, increase in anxiety-like behavior, as well as reductions in monoamine levels and AA hydroxides as the rat age progresses. Regarding the prolonged treatment with different doses of ISOs in middle-aged rats, the results showed that: 1) there were no motor or anxiety-like behavior alterations; 2) there was an improvement in spatial cognitive performance; 3) increase in serum estradiol levels and 4) increase in glutamate and GABA levels in the PFC and hypothalamus. These findings suggest that prolonged treatment with different doses of ISOs could improve spatial cognitive performance and that this effect may be associated with increased estrogen levels, as well as increased levels of glutamate and GABA in the prefrontal cortex and hypothalamus, evidencing a possible neuroprotective effect of ISOs in both regions.

During repetitive stimulation of motor nerve terminals, mitochondrial Ca2+ uptake limits increases in free cytosolic [Ca2+] and helps ensure faithful neuromuscular transmission. Changes in cytosolic [Ca2+] and in mitochondrial [Ca2+] as well as changes in mitochondrial membrane potential (Psi m) were studied in mouse motor nerve terminals using Ca2+ sensitive indicator and potentiometric dyes, respectively. Trains of action potentials (APs) at 50 to 100 Hz produced a rapid increase in mitochondrial [Ca2+] followed by a plateau which usually continued beyond the end of stimulation. After stimulation, mitochondrial [Ca2+] decayed back to baseline over the course of tens of seconds to minutes. Increasing the Ca2+ load delivered to the terminal by increasing the number of stimuli (500-2000), increasing bath [Ca2+], or prolonging the AP with 3,4-diaminopyridine (3-4, DAP, 100 micromolar), prolonged the post-stimulation decay of mitochondrial [Ca2+] without increasing the amplitude of the plateau. Inhibiting openings of the mitochondrial permeability transition pore with cyclosporin A (5 micromolar) had no significant effect on the decay of mitochondrial [Ca2+]. Inhibition of the mitochondrial Na+-Ca2+ exchanger with CGP-37157 (50 micromolar) dramatically prolonged the post-stimulation decay of mitochondrial [Ca2+], reduced post-stimulation residual cytosolic [Ca2+], and reduced the amplitude of end-plate potentials evoked after the end of stimulation. Stimulation-induced mitochondrial Ca2+ uptake resulted in Psi m depolarizations that were small or undetectable at near-physiological temperatures (~30 degrees C). Their amplitude became larger at lower temperatures (~20 degrees C), or when AP duration was increased with 3,4-DAP (20 micromolar). Psi m depolarizations were inhibited by lowering bath [Ca2+] or by blocking P/Q-type Ca2+ channels with omega-agatoxin (0.3 micromolar). Partial inhibition of complex I of the electron transport chain (ETC) with rotenone (50 nM) increased the amplitude of stimulation-induced Psi m depolarizations. These findings suggest that: (1) Ca2+ extrusion from motor terminal mitochondria occurs primarily via the Na+-Ca2+ exchanger and helps sustain post-tetanic transmitter release, and (2) that the depolarization of Psi m that accompanies Ca2+ uptake is limited by accelerated proton extrusion via the ETC.

Background: Achilles tendinopathy is a common clinical syndrome of chronic Achilles tendon pain combined with thickening of the tendon and impaired tendon function. Tendinopathy is often, but not always, induced by mechanical overload, and is frequently accompanied by abnormalities at the tissue level, such as hypercellularity and angiogenesis, in which case the condition is called tendinosis. In tendinosis, there are no signs of intratendinous inflammation, but occasionally increased apoptosis is observed. Tendinosis is often hard to treat and its pathogenesis is still not clear. Recently, a new hypothesis has gained support, suggesting a biochemical model based on the presence of a non-neuronal production of classically neuronal signal substances by the primary tendon cells (tenocytes) in tendinosis. The possible functional importance of these signal substances in tendons is unknown and needs to be studied. In particular, the neuropeptide substance P (SP) and catecholamines are of interest in this regard, since these substances have been found to be up-regulated in tendinosis. As both SP and catecholamines are known to exert effects in other tissues resulting in changes similar to those characteristic of tendinosis, it is possible that they have a role in tendinosis development. It is furthermore unknown what elicits the increased intratendinous neuropeptide production in tendinosis, but given that tendon overload is a prominent riskfactor, it is possible that mechanical stimuli are involved. The hypothesis of this thesis work was that intratendinous production of SP is up-regulated in response to load of Achilles tendons/tenocytes, and thatstimulation of the preferred SP receptor, the neurokinin-1 receptor (NK-1 R), aswell as stimulation of the catecholamine α2 adrenoreceptors, contribute to the hypercellularity seen in tendinosis, via increased proliferation and/or decreased apoptosis, and that SP stimulates tendon angiogenesis. The purpose of the studies was to test this hypothesis. To achieve this, two model systems were used: One in vivo (rabbit Achilles tendon overload model of tendinosis) and one in vitro (human primary Achilles tendon cell culture model). Results: In the rabbit Achilles tendon tissue, SP and NK-1 R expression was extensive in the blood vessel walls, but also to some extent seen in the tenocytes. Quantification of endogenously produced SP in vivo confirmed intratendinous production of the peptide. The production of SP by human tendon cells in vitro was furthermore demonstrated. The catecholamine synthesizing enzyme tyrosine hydroxylase (TH), as well as the α2A adrenoreceptor (α2A AR), were detected in the tenocytes, both in vivo in the rabbit tissue and in vitro in the human tendon cells. As a response to mechanical loading in the in vivo model, the intratendinous levels of SP increased, and this elevation was found to precede distinct tendinosis changes. The in vitro model demonstrated the same response to load, i.e. an increased SP expression, but in this case also a decrease in the NK-1 R expression. In the in vivo model, exogenously administered SP, as well as clonidine (an α2 AR agonist), accelerated tenocyte hypercellularity, an effect that was not seen when administrating a specific α2A AR antagonist. Exogenous administration of SP also resulted in intratendinous angiogenesis and paratendinous inflammation. In the in vitro model, both SP and clonidine had proliferative effects on the human tenocytes, specifically mediated via NK-1R and α2A AR, respectively; both of which in turn involved activation/phosphorylation of the extracellular signal-regulated kinases 1 and 2 (ERK1/2). Exogenously administered SP, in Anti-Fas induced apoptosis of the tenocytes in vitro, confirmed SP to have an anti-apoptotic effect on these cells. This effect was specifically mediated via NK-1 R and the known anti-apoptotic Akt pathway. Conclusions: In summary, this thesis concludes that stimulation of NK-1 R and α2A AR on tenocytes, both in vitro and in vivo, mediates significant cell signalling effects leading to processes known to occur in tendinosis, including hypercellularity. The pathological role of the hypercellularity in tendinosis is still unclear, but it is likely to affect collagen metabolism/turnover and arrangement, and thereby indirectly tendon biomechanical function. Additional evidence is here provided showing that SP not only causes tenocyte proliferation, but also contributes to anti-apoptotic events. Furthermore, it was concluded that SP may be involved in the development of tendinosis, since its production is increased in response to load, preceding tendinosis, and since SP accelerates tendinosis changes, through some mechanistic pathways here delineated. These findings suggest that inhibition of SP, and possibly also catecholamines, could be beneficial in the reconstitution/normalization of tendon structure in tendinosis.

Neurotransmitters are widely distributed in the central nervous system of tilapia during development. In the present study, the effects of gonadal steroids, temperature, and neurotransmitters on the development of central neurotransmitter systems in tilapia, Oreochromis mossambicus, were investigated. Exogenous E2 before 10 days posthatching resulted in an inhibitory effect on the activity of central 5-HT system via decreasing TPH activity and increasing MAO activity, a decrease of the gene expression of brain aromatase and ERa, which is involved in the feminization. The masculinizing actions of 17a-methyltestosterone (MT) are most potent later at up to day 20 of age, and may depend on MT-induction of aromatase activity, aromatase mRNA gene expression and estrogen receptor-b mRNA gene expression. The development of central neurotransmitter systems is influenced by aquatic temperature during its respective restricted period. The influence of both lower and elevated temperatures on the neurotransmitter activity, either increasing or suppressing, is dependent on its developing stage. Neurotransmitters have an effect to influence the development of central neurotransmitter and this effect may mediated by the neural proliferation.

Presynaptic terminals of neurons are optimized for neurotransmitter release, which is tightly controlled by presynaptic calcium. Here, we evaluate the role of calcium influx through voltage-gated calcium channels (VGCCs) in regulating the initial vesicular release probability (p) and the number of vesicles available for release by action potentials (effective RRP) at the calyx of Held synapse in mice. Two established methods of estimating effective RRP size and p reveal that both are calcium dependent. Reducing calcium influx by blocking R-type (VGCCs) or P/Q-type VGCCs also reduces EPSC amplitude via p and effective RRP size. Furthermore, activation of gamma-aminobutryic acid class B (GABAB) receptors, which reduces presynaptic calcium by regulating VGCCs without other significant effects on release, also reduces the effective RRP size and p. These findings suggest that the calcium dependence of RRP size may influence the manner in which certain neuromodulators affect neurotransmitter release.

Inflammatory bowel disease (IBD) alters neuronal regulation of the gastrointestinal (GI) tract. The superior mesenteric ganglia (SMG) contain sympathetic neurons that modulate GI functions such, as motility and blood flow. IBD reduces the release of noradrenaline, a sympathetic neurotransmitter. We hypothesized that the reduction in NA release is due to inhibition of voltage-gated calcium current (ICa), as calcium influx is a regulator of neurotransmitter release. We also hypothesized that tumor necrosis factor α (TNFα), a proinflammatory cytokine elevated during IBD, can also inhibit the ICa of SMG neurons. Therefore, we compared ICa amplitude in neurons from normal mice and mice with dextran sulphate sodium (DSS; 5% w/v)-induced colitis. Neurons dissociated from the SMG were cultured overnight and changes to ICa were investigated using electrophysiological, Ca2+ imaging, PCR and neurotransmitter release techniques. Colitis significantly reduced ICa of SMG neurons by selectively inhibiting N-type Ca2+ channels. This was accompanied by a reduction in mRNA encoding the N-type channel alpha subunit (CaV 2.2) and a rightward shift in the voltage dependence of activation of ICa. Colitis reduced the NA release from the colon and jejunum. Depolarization-induced release of tritiated-NA was inhibited by ω-Conotoxin GVIA (300 nM). These results suggest that the changes in VGCC observed at the cell bodies of SMG neurons were also occurring at the nerve terminals during colitis. Similar experimental techniques were performed using SMG neurons incubated overnight in TNFα (1nM). TNFα decreased ICa and depolarization-induced Ca2+ influx in SMG neurons. Similar to DSS-induced colitis, the reduction in ICa was limited to N-type Ca2+ channels. Preincubation of neurons with SC 514 (20μM) and Bay 11 7082 (1µM), inhibitors of nuclear factor kappa B signaling, prevented the reduction in ICa. Preincubation with the p38 MAPK inhibitor, PD 169316 (30µM), recovered a smaller portion of the reduction in Ca2+ influx. These data suggest that DSS colitis and TNFα inhibit N-type VGCC ICa in sympathetic neurons and identify a novel role for NF-κB and p38 MAPK in the regulation of neurotransmitter release. These findings also suggest that DSS colitis inhibits NA release by altering sympathetic N-type VGCC in the colon and jejunum. / Thesis (Master, Physiology) -- Queen's University, 2008-09-02 12:06:20.438