After unilateral lesions of the mesotelencephalic dopamine (DA) system, the administration of DA receptor agonists results in circling. This response is believed to reflect an asymmetry in mesotelencephalic DA activity. Moreover, drug-induced circling is thought to be directed away from the projection of higher dopaminergic activity. Recently, it has been reported that circling can be established and maintained using operant procedures in surgically intact and drug naive rats. The phenomenon of conditioned circling has been associated with an asymmetrical change in DA metabolism within the striatum and nucleus accumbens. The present series of experiments was designed to characterize further the involvement of mesotelencephalic DA in conditioned circling. Rats trained to circle for water according to a continuous schedule of reinforcement did not exhibit increased DA metabolism within either the striatum or the nucleus accumbens (Experiment I). However, a bilateral augmentation was observed when rates of responding were increased by implementing an intermittent schedule of reinforcement (Experiment II). Concurrent increases in the biosynthesis of DA, as estimated by accumulation of DOPA following the administration of a DOPA decarboxylase inhibitor, were not observed (Experiment III). Experiments IVa and IVb examined the extent to which inherent directional biases, which play a role in determining the magnitude and direction of drug-induced circling, influenced the acquisition and performance of the conditioned circling response. No effects were evident. Moreover, a symmetrical, bilateral enhancement in DA metabolism was observed in the striatum, irrespective of directional preferences. While conditioned circling can be established and maintained by reinforcing the response with food, food itself influenced DA metabolism and therefore precluded the detection of changes in DA metabolism specific to the circling response. Specifically, striatal and accumbens DA metabolism was augmented to a similar extent in animals given matched amounts of non-contingently presented food (Experiment V). Concentrations of DA, DOPAC and homovanillic acid (HVA) were found to be differentially distributed throughout the striatum (Experiment Via), suggesting a possible chemical basis for the heterogeneity of striatal DAergic functions. Changes in striatal DA metabolism associated with conditioned circling were observed only within localized regions of the anterior striatum (Experiment VIb). All changes noted were, however, bilateral in nature. Finally, unilateral lesions of the mesotelencephalic DA projection, following the establishment of the conditioned circling response, disrupted responding, irrespective of the relative locus of the lesion (i.e. ipsilateral or contralateral to the direction of turning) (Experiment VII). However, the extent of the behavioral deficit was more severe following contralaterally placed lesions. It is concluded that circling, established and maintained by positive reinforcement, is subserved by a bilateral augmentation in DA metabolism within the nucleus accumbens and discrete regions of the striatum. However, lesion studies indicate an asymmetrical involvement of the ipsilateral and contralateral projections in this response. / Medicine, Faculty of / Graduate

A procedure was developed to determine the effect of a dopamine (DA) antagonist (haloperidol) and a DA agonist (d-amphetamine) on rats' perceptions of the hedonic value of food. Eighteen rats were trained to discriminate between two quantities of sweet food pellets (1 and 4), in a forced-choice two-lever successive discrimination procedure. To control for non-specific perceptual effects of the treatments, the rats were also trained to discriminate between 1 and 4 tones. It was established that rats attended to the value of food, as well as the proportional differences in quantity, when discriminating food quantities. This was accomplished by altering the value of the food in two ways. Firstly, "hunger" was altered by changing the degree of food deprivation during testing. Secondly, unsweetened food pellets were introduced as probe cues. These two methods of altering the value of food pellets were utilized while quantity generalization gradients were determined, by presenting animals with 1,2, 3 and 4 numbers of stimuli as probe cues. Two measures were derived from these generalization gradients: the point of subjective equality (PSE), which is the calculated number of stimuli that would maintain responses equally distributed between the two levers, and the slope of the gradient. The PSE primarily reflects perceptual processes, while the slopes of the gradients provide an index of performance impairment. It was observed that decreasing the value of food by either decreasing food deprivation or reducing the sweetness of the food pellets resulted in the rats perceiving a given quantity of food as larger than before these treatments (decreased the food PSE). Neither altering food deprivation nor introducing novel tone probes had an effect on the numerical attributes of tones, as reflected by the tone PSE. Haloperidol (0.030, 0.50 and 0.083 mg/kg, i.p.) produced a statistically significant, but slight dose-dependent performance deficit, as reflected by the slope of the generalization gradients. It did not affect the perception of food pellet quantities at any dose, as reflected by the food PSE. Haloperidol decreased the number of tones a given quantity was perceived as by rats (increased the tone PSE). Amphetamine (0.25, 0.50 and 1.0 mg/kg, i.p.) decreased the perception of a given quantity of food (increased the food PSE) in a dose-dependent manner, without a significant effect on performance. Thus, amphetamine enhanced the hedonic value of food. Amphetamine also increased rats' perceptions of a given number of tones (decreased the tone PSE). It therefore appears that while d-amphetamine can enhance the perceived hedonic value of food, haloperidol has no effect on rats' perceptions of the hedonic value of food. Furthermore, evidence that DA systems are involved in the mechanism of an "internal clock" or "counter" was obtained. / Medicine, Faculty of / Graduate

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

Yuen Chi Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 84-106). / Abstracts in English and Chinese. / Abstract (in English) --- p.ii / Abstract (in Chinese) --- p.iv / Acknowledgement --- p.vi / Table of Contents --- p.vii / List of Figures --- p.xii / Symbols and Abbreviations --- p.xv / Scientific names --- p.xvii / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1.1 --- Pituitary --- p.1 / Chapter 1.2 --- Gonadotropins (GTHs) --- p.3 / Chapter 1.2.1 --- Structure --- p.3 / Chapter 1.2.2 --- Function --- p.5 / Chapter 1.2.3 --- Regulation --- p.7 / Chapter 1.2.3.1 --- Neuroendocrine hypothalamic regulators --- p.9 / Chapter 1.2.3.1.1 --- Gonadotropin-releasing hormone (GnRH) --- p.9 / Chapter 1.2.3.1.2 --- Dopamine (DA) --- p.11 / Chapter 1.2.3.2 --- Endocrine regulators from the gonads --- p.12 / Chapter 1.2.3.2.1 --- Gonadal steroids (T and E2) --- p.12 / Chapter 1.2.3.2.2 --- Negative steroid effect on pituitary GTH regulation --- p.12 / Chapter 1.2.3.2.3 --- Positive steroid effect on pituitary GTH regulation --- p.13 / Chapter 1.2.3.3 --- Paracrine regulators from within the pituitary --- p.14 / Chapter 1.3 --- Activin --- p.14 / Chapter 1.3.1 --- Structure --- p.14 / Chapter 1.3.2 --- Function --- p.16 / Chapter 1.4 --- Follistatin (FS) --- p.17 / Chapter 1.4.1 --- Structure --- p.17 / Chapter 1.4.2 --- Function --- p.19 / Chapter 1.5 --- Temporal Variations in the GTH Expressional and Releasing Profile and Sex Steroid Level in the Goldfish --- p.19 / Chapter 1.5.1 --- Hormone changes during annual cycle --- p.20 / Chapter 1.5.2 --- Hormone changes during ovulatory cycle --- p.21 / Chapter 1.6 --- Objectives of the Present Study --- p.23 / Chapter Chapter 2 --- "Effects of Dopamine on the Expression of Gonadotropin (GTH) Subunits in the Dispersed Pituitary Cells of the Goldfish, Carassius auratus" --- p.26 / Chapter 2.1 --- Introduction --- p.26 / Chapter 2.2 --- Materials and Methods --- p.27 / Chapter 2.2.1 --- Materials --- p.27 / Chapter 2.2.2 --- Primary culture of dispersed goldfish pituitary cells --- p.28 / Chapter 2.2.3 --- mRNA analysis --- p.29 / Chapter 2.2.4 --- Data analysis --- p.30 / Chapter 2.3 --- Results --- p.30 / Chapter 2.3.1 --- Effects of DA on GTH-Iβ and GTH-IIβ expression --- p.30 / Chapter 2.3.2 --- Effects of DA D1 and D2 agonists on GTH-Iβ expression --- p.33 / Chapter 2.3.3 --- Effects of DA D1 and D2 antagonists on DA- inhibited GTH-Iβ expression --- p.33 / Chapter 2.3.4 --- Effects of α-adrenergic agonists on GTH-Iβ expression --- p.33 / Chapter 2.4 --- Discussion --- p.37 / Chapter Chapter 3 --- Seasonal Variation of Activin-regulated Goldfish Pituitary GTH-Ip and GTH-IIβ Expression and Evidence for the Involvement of Gonadal Steroids --- p.40 / Chapter 3.1 --- Introduction --- p.40 / Chapter 3.2 --- Materials and Methods --- p.42 / Chapter 3.2.1 --- Materials --- p.42 / Chapter 3.2.2 --- Gonadectomy of the goldfish --- p.42 / Chapter 3.2.3 --- Primary culture of dispersed pituitary cells --- p.43 / Chapter 3.2.4 --- mRNA analysis --- p.43 / Chapter 3.2.5 --- Data analysis --- p.44 / Chapter 3.3 --- Results --- p.44 / Chapter 3.3.1 --- Effects of goldfish activin B on the expression of GTH-Iβ and GTH-IIβ --- p.44 / Chapter 3.3.2 --- Seasonal variation of activin-regulated expression of GTH-Iβ and GTH-IIβ --- p.45 / Chapter 3.3.3 --- Effects of gonadectomy on basal and activin- regulated expression of GTH-Iβ and GTH-IIβ --- p.45 / Chapter 3.3.4 --- Effects of sex steroids on basal and activin- regulated expression of GTH-Iβ and GTH-IIβ in vitro --- p.50 / Chapter 3.4 --- Discussion --- p.57 / Chapter Chapter 4 --- Evidence for the Autocrine/Paracrine Regulation of Gonadotropin Expression by Activin in the Goldfish Pituitary --- p.61 / Chapter 4.1 --- Introduction --- p.61 / Chapter 4.2 --- Materials and Methods --- p.63 / Chapter 4.2.1 --- RNA isolation --- p.63 / Chapter 4.2.2 --- Reverse transcription-polymerase chain reaction (RT-PCR) --- p.63 / Chapter 4.2.3 --- Primary culture of goldfish pituitary cells --- p.63 / Chapter 4.2.4 --- Slot-blot analysis --- p.64 / Chapter 4.2.5 --- Data analysis --- p.64 / Chapter 4.3 --- Results --- p.65 / Chapter 4.3.1 --- Expression of activin βB subunit and activin type IEB receptor in the goldfish pituitary --- p.65 / Chapter 4.3.2 --- Effects of human activin A on goldfish GTH-Iβ and GTH-IIβ expression --- p.65 / Chapter 4.3.3 --- Effects of follistatin on basal and activin- regulated GTH-Iβ and GTH-IIβ expression --- p.69 / Chapter 4.4 --- Discussion --- p.69 / Chapter Chapter 5 --- General Discussion --- p.77 / Chapter 5.1 --- Overview --- p.77 / Chapter 5.2 --- Contribution of the Present Study --- p.78 / Chapter 5.2.1 --- Dopamine as a potential neuroendocrine regulator in the differential regulation of GTH-Iβ and GTH-IIβ expression --- p.78 / Chapter 5.2.2 --- Seasonal variation of the effects of activin on GTH-Iβ and GTH-IIβ expression --- p.79 / Chapter 5.2.3 --- Autocrine/paracrine regulation of GTH expression by activin --- p.79 / Chapter 5.3 --- Future Prospects --- p.81 / References --- p.84

The involvement of dopamine in anticipatory and consummatory aspects of feeding behaviors was investigated in the present thesis. All measurements of dopaminergic activity were taken by in vivo electrochemical techniques. In Experiment 1, dopamine efflux in the nucleus accumbens and caudate of male rats was monitored during sessions in which a small, unsignalled liquid meal was consumed. Increases in the electrochemical measure of dopamine activity, which were of similar temporal pattern and magnitude, were observed in both the nucleus accumbens and striatum following meal consumption. These data suggest a possible postingestional role of dopamine in these two brain structures. In Experiment 2, a conditioned feeding paradigm was utilized to study the role of dopamine during a discrete anticipatory phase of feeding. Rats were conditioned to discriminate between a positive conditioned stimulus (CS+) predictive of meal delivery, and a negative conditioned stimulus (CS-) that was not associated with food. Increases in dopamine activity, as determined by changes in electrochemical oxidation currents, were found to be greater during the CS+ than during the CS- in both the nucleus accumbens and caudate. In addition, the magnitude of increase was greater in the nucleus accumbens than the caudate, suggesting that the accumbens may be preferentially involved in the processing of external incentive stimuli. The results support a role for dopamine in both the nucleus accumbens and caudate during appetitive or anticipatory responding for food in the male rat. / Medicine, Faculty of / Graduate