No description available.

Note:

No / Nursing has reciprocal benefits for both mother and infant, helping to promote maternal behavior and bonding. To test the "rewarding" nature of nursing, functional magnetic resonance imaging was used to map brain activity in lactating dams exposed to their suckling pups versus cocaine. Suckling stimulation in lactating dams and cocaine exposure in virgin females activated the dopamine reward system. In contrast, lactating dams exposed to cocaine instead of pups showed a suppression of brain activity in the reward system. These data support the notion that pup stimulation is more reinforcing than cocaine, underscoring the importance of pup seeking over other rewarding stimuli during lactation

Parkinson's disease is characterized by progressive degeneration of substantia nigra (SN) and subsequently loss of the nigrostriatal circuit. Many strategies have attempted to reconstruct this circuit but failed to satisfy clinical trials. The inhibitory environment of the adult CNS and the long distance between the SN and the striatum make true reconstruction difficult. To reconstruct this circuit, we used a transplant-pathway targeting model. Several putative pathway targeting molecules were examined for their ability to direct the growth of axons from a dopaminergic transplant. For a proof-of-principle study, adenoviral and lentiviral encoded glial cell line-derived neurotrophic factor (GDNF), GDNF-receptor alpha1 (GFRa1 ), or netrin-1 were injected along the corpus callosum individually or in combination. Treatment with individual factors leads to modest growth with few axons extending the entire length of the pathway. Combined treatment with either GDNF/GFRa1 or GDNF/netrin-1 induced the most robust growth towards the contralateral striatum. GDNF/netrin-1 showed the most consistent growth, with about 80% of the axons growing to the farthest injection site on the contralateral side. To determine if this combination of guidance molecules could be used to reconstruct the nigrostriatal pathway, we examined axon outgrowth from transplants placed within the SN in the 6-0HDA-Iesioned hemiparkinsonian animal model. A pathway from the SN to the striatum was made by injecting lentivirus encoding either GDNF and netrin-1 or GDNF and GFRa1, along the internal capsule, from the SN to the striatum. In another cohort of animals lentivirus encoding GFP was used as a control. A piece of embryonic VM tissue was transplanted into the SN two weeks after lentivirus injections. Compare to the GFP control group, a significantly greater number of dopaminergic axons grew from the transplants towards the striatum ten weeks after transplantation. Retrograde tract tracing showed the dopaminergic axons were from A9 cells in the transplant. Behavioral studies showed a significant reduction in number of amphetamine-induced rotations in GDNF/netrin-1 treated animals. Functional recovery strongly correlated with the number of dopaminergic fibers growing out from the transplant. This study shows that a functional nigrostriatal pathway can be reconstructed by guiding axonal growth from the dopaminergic neurons transplanted in the SN along a preformed growth-supportive pathway extending into the striatum. Refinement of this technique could be beneficial for PD patients in the future.

The classic rodent model of Parkinson’s disease (PD) is produced by unilateral lesioning of pars compacta substantia nigra (SNpc) in adult rats, producing unilateral motor deficits which can be assessed by dopamine (DA) D2 receptor (D2-R) agonist induction of measurable unilateral rotations. Bilateral SNpc lesions in adult rats produce life-threatening aphagia, adipsia, and severe motor disability resembling paralysis-a PD model that is so compromised that it is seldom used. Described in this paper is a PD rodent model in which there is bilateral 99% loss of striatal dopaminergic innervation, produced by bilateral intracerebroventricular or intracisternal 6-hydroxydopamine (6-OHDA) administration to perinatal rats. This procedure produces no lethality and does not shorten the life span, while rat pups continue to suckle through the pre-weaning period; and eat without impairment post-weaning. There is no obvious motor deficit during or after weaning, except with special testing, so that parkinsonian rats are indistin-guishable from control and thus allow for behavioral assessments to be conducted in a blinded manner. L-DOPA (L-3,4-dihydroxyphenylalanine) treatment increases DA content in striatal tissue, also evokes a rise in extraneuronal (i.e.,in vivo microdialysate) DA, and is able to evoke dyskinesias. D2-R agonists produce effects similar to those of L-DOPA. In addition, effects of both D1-and D2-R agonist effects on overt or latent receptor supersensitization are amenable to study. Elevated basal levels of reactive oxygen species (ROS), namely hydroxyl radical, occurring in dopaminergic denervated striatum are suppressed by L-DOPA treatment. Striatal serotoninergic hyperinnervation ensuing after perinatal dopaminergic denervation does not appear to interfere with assessments of the dopaminergic system by L-DOPA or D1-or D2-R agonist challenge. Partial lesioning of serotonin fibers with a selective neurotoxin either at birth or in adulthood is able to eliminate sero-toninergic hyperinnervation and restore the normal level of serotoninergic innervation. Of all the animal models of PD, that produced by perinatal 6-OHDA lesioning provides the most pronounced destruction of nigrostriatal neurons, thus representing a model of severe PD, as the neurochemical outcome resembles the status of severe PD in humans but without obvious motor deficits.

La queue de l’aire tegmentale ventrale (tVTA) est le principal contrôle inhibiteur des neurones dopaminergiques du mésencéphale. Cette structure, bien qu’aujourd’hui très étudiée, n’est cependant pas encore référencée dans les atlas stéréotaxiques. Anatomiquement, nous avons pu apporter une définition de référence de la tVTA, à travers son analyse neurochimique, stéréologique, hodologique et génomique. Fonctionnellement, nous avons montré son rôle dans la réponse à des expériences émotionnelles aversives et nous avons testé son influence sur les symptômes moteurs et non-moteurs de la maladie de Parkinson. Nous avons ainsi montré qu’une co-lésion de la tVTA dans un modèle murin de la maladie permet une amélioration des performances motrices, des seuils nociceptifs et des symptômes de type dépressifs. Ce travail a ainsi participé au progrès de nos connaissances sur la tVTA et ouvre de nouvelles pistes d’exploration quant à son implication fonctionnelle. / The tail of the ventral tegmental area (tVTA) is the major brake of the midbrain dopamine neurons. This structure although studied, is not yet referenced in stereotaxic atlases. Anatomically, this work allowed to obtain a reference definition of the tVTA through its neurochemical, stereological, connectivity-based and genomic analyses. Functionally, we studied its role for the response of aversive stimuli and we tested its influence on motor and non-motor symptoms of Parkinson’s disease. We observed that a co-lesion of the tVTA in a rodent model of the disease induce motor, nociceptive and depressive-like symptoms improvements. This work has thus contributed to the progress of our knowledge on the tVTA and opens new explorative track for its functional implication.

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, characterized pathologically by a marked loss of dopaminergic nigrostriatal neurons and clinically by disabling movement disorders. PD can be treated by inhibiting monoamine oxidase (MAO), specifically MAO–B, since this is a major enzyme involved in the catabolism of dopamine in the substantia nigra of the brain. Inhibition of MAO–B may conserve the dopamine supply in the brain and may therefore provide symptomatic relief for PD patients. Selegiline is an irreversible MAO–B inhibitor and is currently used for the treatment of PD. Irreversible inhibitors inactivate enzymes by forming stable covalent complexes. The process is not readily reversed either by removing the remainder of the free inhibitor or by increasing the substrate concentration. Even dilution or dialysis does not dissociate the enzyme inhibitor complex and restore enzyme activity. From a safety point of view it may therefore be more desirable to develop reversible inhibitors of MAO–B. In this study, caffeine was used as lead compound to design, synthesize and evaluate new reversible inhibitors of MAO–B. This study is based on the finding that C–8 substituted caffeine analogues are potent MAO inhibitors. For example, (E)–8–(3–chlorostyryl)caffeine (CSC) is an exceptionally potent competitive inhibitor of MAO–B with an enzyme–inhibitor dissociation constant (Ki value) of 128 nM. In this study caffeine was similarly conjugated at C–8 to various side–chains. The effect that these chosen side–chains had on the MAO–B inhibition activity of C–8 substituted caffeine analogues will then be evaluated. The caffeine analogues were also evaluated as human MAO–A inhibitors. For the purpose of this study, saturated C–8 side chains were selected with the goal of discovering new C–8 side chains that enhance the MAO–A and ?B inhibition potency of caffeine. As mentioned above, the styryl side chain is one example of a side chain that enhances the MAO–B inhibition potency of caffeine. Should a side chain with promising MAO inhibition activity be identified in this study, the inhibition potency will be further optimized in a future study by the addition of a variety of substituents to the C–8 side chain ring. For example, halogen substitution of (E)–8– styrylcaffeine enhances the MAO–B inhibition potency by up to 10 fold. The saturated side chains selected for the present study included the phenylethyl (1), phenylpropyl (2), phenylbutyl (3) and phenylpentyl (4) functional groups. Also included are the cyclohexylethyl (8), 3–oxo–3– phenylpropyl (5), 4–oxo–4–phenylbutyl (6) moieties. A test compound containing an unsaturated linker between C–8 of caffeine and the side chain ring, the phenylpropenyl analogue 7, was also included. This study is therefore an exploratory study to discover new C–8 moieties that are favorable for MAO– inhibition. All the target compounds were synthesized by reacting 1,3–dimethyl–5,6–diaminouracil with an appropriate carboxylic acid in the presence of a carbodiimide dehydrating agent. Following ring closure and methylation at C–7, the target inhibitors were obtained. Inhibition potencies were determined using recombinant human MAO–A and MAO–B as enzyme sources. The inhibitor potencies were expressed as IC50 values. The most potent MAO–B inhibitor was 8–(5– phenylpentyl)caffeine (4) with an IC50 value of 0.656 ?M. In contrast, all the other test inhibitors were moderately potent MAO–B inhibitors. In fact the next best MAO–B inhibitor, 8–(4– phenylbutyl)caffeine (3) was approximately 5 fold less potent than 4 with an IC50 value of 3.25 ?M. Since the 5–phenylpentyl moiety is the longest side chain evaluated in this study, this finding demonstrates that longer C–8 side chains are more favorable for MAO–B inhibition. Interestingly, compound 5 containing a cyclohexylethyl side chain (IC50 = 6.59 ?M) was approximately 4 fold more potent than the analogue containing the phenylethyl linker (1) (IC50 = 26.0 ?M). This suggests that a cyclohexyl ring in the C–8 side chain of caffeine may be more optimal for MAO–B inhibition and should be considered in future studies. The caffeine analogues containing the oxophenylalkyl side chains (5 and 6) were weak MAO–B inhibitors with IC50 values of 187 ?M and 46.9 ?M, respectively. This suggests that the presence of a carbonyl group in the C–8 side chain is not favorable for the MAO–B inhibition potency of caffeine. The unsaturated phenylpropenyl analogue 7 was also found to be a relatively weak MAO–B inhibitor with an IC50 value of 33.1 ?M. In contrast to the results obtained with MAO–B, the test caffeine analogues were all weak MAOA inhibitors. With the exception of compound 5, all of the analogues evaluated were selective inhibitors of MAO–B. The most potent MAO–B inhibitor, 8–(5–phenylpentyl)caffeine (4) was the most selective inhibitor, 48 fold more potent towards MAO–B than MAO–A. This study also shows that two selected analogues (5 and 3) bind reversibly to MAO–A and ?B, respectively, and that the mode of MAO–A and –B inhibition is competitive for these representative compounds. / Thesis (M.Sc. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2011.

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, characterized pathologically by a marked loss of dopaminergic nigrostriatal neurons and clinically by disabling movement disorders. PD can be treated by inhibiting monoamine oxidase (MAO), specifically MAO–B, since this is a major enzyme involved in the catabolism of dopamine in the substantia nigra of the brain. Inhibition of MAO–B may conserve the dopamine supply in the brain and may therefore provide symptomatic relief for PD patients. Selegiline is an irreversible MAO–B inhibitor and is currently used for the treatment of PD. Irreversible inhibitors inactivate enzymes by forming stable covalent complexes. The process is not readily reversed either by removing the remainder of the free inhibitor or by increasing the substrate concentration. Even dilution or dialysis does not dissociate the enzyme inhibitor complex and restore enzyme activity. From a safety point of view it may therefore be more desirable to develop reversible inhibitors of MAO–B. In this study, caffeine was used as lead compound to design, synthesize and evaluate new reversible inhibitors of MAO–B. This study is based on the finding that C–8 substituted caffeine analogues are potent MAO inhibitors. For example, (E)–8–(3–chlorostyryl)caffeine (CSC) is an exceptionally potent competitive inhibitor of MAO–B with an enzyme–inhibitor dissociation constant (Ki value) of 128 nM. In this study caffeine was similarly conjugated at C–8 to various side–chains. The effect that these chosen side–chains had on the MAO–B inhibition activity of C–8 substituted caffeine analogues will then be evaluated. The caffeine analogues were also evaluated as human MAO–A inhibitors. For the purpose of this study, saturated C–8 side chains were selected with the goal of discovering new C–8 side chains that enhance the MAO–A and ?B inhibition potency of caffeine. As mentioned above, the styryl side chain is one example of a side chain that enhances the MAO–B inhibition potency of caffeine. Should a side chain with promising MAO inhibition activity be identified in this study, the inhibition potency will be further optimized in a future study by the addition of a variety of substituents to the C–8 side chain ring. For example, halogen substitution of (E)–8– styrylcaffeine enhances the MAO–B inhibition potency by up to 10 fold. The saturated side chains selected for the present study included the phenylethyl (1), phenylpropyl (2), phenylbutyl (3) and phenylpentyl (4) functional groups. Also included are the cyclohexylethyl (8), 3–oxo–3– phenylpropyl (5), 4–oxo–4–phenylbutyl (6) moieties. A test compound containing an unsaturated linker between C–8 of caffeine and the side chain ring, the phenylpropenyl analogue 7, was also included. This study is therefore an exploratory study to discover new C–8 moieties that are favorable for MAO– inhibition. All the target compounds were synthesized by reacting 1,3–dimethyl–5,6–diaminouracil with an appropriate carboxylic acid in the presence of a carbodiimide dehydrating agent. Following ring closure and methylation at C–7, the target inhibitors were obtained. Inhibition potencies were determined using recombinant human MAO–A and MAO–B as enzyme sources. The inhibitor potencies were expressed as IC50 values. The most potent MAO–B inhibitor was 8–(5– phenylpentyl)caffeine (4) with an IC50 value of 0.656 ?M. In contrast, all the other test inhibitors were moderately potent MAO–B inhibitors. In fact the next best MAO–B inhibitor, 8–(4– phenylbutyl)caffeine (3) was approximately 5 fold less potent than 4 with an IC50 value of 3.25 ?M. Since the 5–phenylpentyl moiety is the longest side chain evaluated in this study, this finding demonstrates that longer C–8 side chains are more favorable for MAO–B inhibition. Interestingly, compound 5 containing a cyclohexylethyl side chain (IC50 = 6.59 ?M) was approximately 4 fold more potent than the analogue containing the phenylethyl linker (1) (IC50 = 26.0 ?M). This suggests that a cyclohexyl ring in the C–8 side chain of caffeine may be more optimal for MAO–B inhibition and should be considered in future studies. The caffeine analogues containing the oxophenylalkyl side chains (5 and 6) were weak MAO–B inhibitors with IC50 values of 187 ?M and 46.9 ?M, respectively. This suggests that the presence of a carbonyl group in the C–8 side chain is not favorable for the MAO–B inhibition potency of caffeine. The unsaturated phenylpropenyl analogue 7 was also found to be a relatively weak MAO–B inhibitor with an IC50 value of 33.1 ?M. In contrast to the results obtained with MAO–B, the test caffeine analogues were all weak MAOA inhibitors. With the exception of compound 5, all of the analogues evaluated were selective inhibitors of MAO–B. The most potent MAO–B inhibitor, 8–(5–phenylpentyl)caffeine (4) was the most selective inhibitor, 48 fold more potent towards MAO–B than MAO–A. This study also shows that two selected analogues (5 and 3) bind reversibly to MAO–A and ?B, respectively, and that the mode of MAO–A and –B inhibition is competitive for these representative compounds. / Thesis (M.Sc. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2011.

Made available in DSpace on 2016-06-02T19:22:56Z (GMT). No. of bitstreams: 1 4388.pdf: 1226815 bytes, checksum: 90cf9ba0ac00628538f6b744e2c5bac1 (MD5) Previous issue date: 2011-02-25 / Financiadora de Estudos e Projetos / Estrogen is a steroid hormone known to play a role in cellular events important for development, maintenance of body physiology and modulatory actions on central nervous system during life. The aim of this study was to investigate the effect of ovariectomy (OVX) and the intervention of strength training on the tissue concentrations of dopamine (DA) and serotonin (5-HT) in the nigrostriatal and mesolimbic pathways in female rats. Also, check behavioral parameters of exploratory activity in novel environment, in testing of the plus maze (EPM) and open field (CA). Female rats were divided into four groups: Sedentary (Sed- Intact), ovariectomized Sedentary (Sed-OVX) Trained intact (Intact-ExCrônico) Trained ovariectomized (OVX-ExCrônico) (n = 10 per group). We conducted a period of 12 weeks of strength training which consisted of increases in a vertical ladder of 1.1 meters, weight tied to its tail. The sessions were held once every three days with 4-9 and 8-12 uphill climb for motion. The OVX caused changes in tissue concentrations of DA and 5-HT in the mesolimbic and nigrostriatal pathways. However strength training has not been able to revet these changes. In behavioral tests of anxiety were observed behavior and decrease the exploratory activity of rats in the independent training (OVX). The results of this study showed that OVX alters the state of the tissue concentrations of DA and 5-HT but these changes seem to depend on the type of receptor and its topographic distribution. Strength training has not been able to reverse these changes. / O estrogênio é um hormônio esteróide conhecido por representar um papel relevante nos eventos celulares do desenvolvimento, manutenção da fisiologia do corpo e ações moduladoras no sistema nervoso central (SNC) durante a vida. O objetivo do presente estudo foi investigar o efeito da ovariectomia (OVX) e da intervenção do treinamento de força sobre as concentrações teciduais de dopamina (DA) e serotonina (5- HT) nas Vias Nigroestriatal e Mesolímbicas em ratas. Além disso, verificar parâmetros comportamentais de atividade exploratória em ambiente novo, nos testes do labirinto em cruz elevado (LCE) e campo aberto (CA). Ratas fêmeas foram divididas em quarto grupos: Sedentário (Sed-Intacto); Sedentário ovariectomizado (Sed-OVX); Treinado intacto (ExCrônico-Intacto); Treinado ovariectomizado (ExCrônico-OVX) (n = 10 por grupo). Foi realizado um período de 12 semanas de treinamento de força que consistia em subidas em uma escada vertical de 1,1 metros, com peso atado a cauda. As sessões foram realizadas uma vez a cada três dias com 4-9 subidas e 8-12 movimentos por escalada. A OVX causou alterações na concentração tecidual de DA e 5-HT nas Vias Mesolímbica e Nigroestriatal . No entanto o treinamento de força não foi capaz de reverter essas alterações. Nos testes comportamentais foi observado comportamento de ansiedade e decréscimo da atividade exploratória dos animais submetidos ao treinamento, independente da OVX. Os resultados deste estudo mostram que o estado de OVX altera as concentrações teciduais de DA e 5- HT, no entanto essas alterações parecem depender do tipo de receptor e da sua distribuição topográfica. O treinamento de força não foi capaz de reverter essas alterações.

Au-delà des symptômes moteurs, la maladie de Parkinson (MP) est également caractérisée par une myriade de symptômes neuropsychiatriques allant de l’apathie et la dépression aux troubles du contrôle des impulsions (TCI). Les TCI représentent un groupe d’addictions comportementales incluant le jeu pathologique, l’hypersexualité et les achats faits de manière compulsive. Observés chez 10 à 14 % des patients parkinsoniens sous traitement dopaminergique, ils affectent fortement leur qualité de vie. L’impulsivité cognitive reflétant notamment l’incapacité à tolérer les délais de renforcements, est au cœur des TCI. En effet, différentes études suggèrent que cette impulsivité serait exacerbée dans la MP et sous traitements dopaminergiques. Cependant, les mécanismes sous-tendant les TCI dans la MP demeurent méconnus, et la contribution respective de la lésion, du traitement dopaminergique, et de certains facteurs de vulnérabilité reste à déterminer. De plus, l’impulsivité d’attente, une autre forme de déficit d’inhibition qui peut conduire au développement de comportements compulsifs, a été peu étudiée dans le cadre des TCI.L’objectif de ce projet de thèse a été d’évaluer l’influence d’une dénervation dopaminergique de la voie nigrostriée, avec ou sans adjonction d’agoniste dopaminergique, sur le développement d’impulsivité. Pour cela, nous avons utilisé un modèle lésionnel des troubles non-moteurs de la MP. Ces rats ont reçu une injection bilatérale de neurotoxine 6-OHDA dans la SNc, afin d’induire une dénervation sélective, bilatérale et partielle du striatum dorsal. Ils ont ensuite été traités avec du pramipexole, un agoniste des récepteurs D2/3, connu pour favoriser le développement de TCI chez les patients parkinsoniens. Les tâches d’intolérance au délai et de réaction en série à 5 choix (5-CSRTT) ont été utilisées pour évaluer respectivement l’impulsivité cognitive et l’impulsivité d’attente. Dans le premier paradigme, les rats doivent appuyer sur un levier pour choisir entre une petite récompense immédiate, ou une plus grosse récompense, avec un un délai. Dans le second paradigme, ils doivent inhiber l’émission d’une réponse motrice jusqu’à l’apparition d’un stimulus lumineux. Le traitement chronique au pramipexole augmente considérablement les choix impulsifs effectués dans la tâche d’intolérance au délai, mais seulement chez les rats non lésés. En effet, la lésion dopaminergique seule ou avec le traitement ne favorise pas les comportements impulsifs. Dans la tâche de 5-CSRTT, le pramipexole semble également promouvoir l’émission de réponses prématurées (effet pro-impulsif), lorsque l’intervalle inter-essais est constant. Cependant, lorsque cet intervalle augmente, le pramipexole provoque à l’inverse une diminution des réponses prématurées (effet anti-impulsif). Cette modulation d’impulsivité étant seulement observée chez les rats hautement impulsifs, ceci suggère qu’un endophénotype impulsif puisse être un facteur de vulnérabilité à l’effet iatrogène du pramipexole.A l’échelle neuronale, ce traitement favorise la surexpression des ARNm codants pour les récepteurs dopaminergiques D2 dans le striatum et y modifie la connectivité glutamatergique telle qu’observée en microscopie électronique. De plus, nous avons observé une suractivation de la voie mTORC1 dans le noyau accumbens, comme déjà constaté dans les processus addictifs. Afin d’apporter un lien causal à cette étude, nous avons bloqué l’activité de la voie mTORC1 par un inhibiteur spécifique, la rapamycine, chez des rats traités au pramipexole. Etonnamment, cette combinaison accentue fortement l’intolérance au délai, alors que la rapamycine seule ne provoque aucun effet notable. Ceci pourrait s’expliquer par une cinétique d’activation et d’inhibition complexe de cette voie. L’ensemble de ces résultats suggère que l’impulsivité observée dans la MP serait causée par une action iatrogène du pramipexole via une activation anormale de la voie mTORC1 dans le noyau accumbens. / Beyond motor symptoms, Parkinson’s disease (PD) is also characterized by a plethora of neuropsychiatric deficits, ranging from apathy and depression to Impulse control disorders (ICDs). ICDs represent a complex group of behavioral addictions including gambling disorders, hypersexuality and compulsive shopping, displayed by 10 to 14% of PD patients under dopamine replacement therapies, whose quality of life is greatly diminished. Importantly, cognitive impulsivity reflecting in particular, an inability to tolerate delays to reinforcements, appears as a core symptom of ICDs. Indeed, recent evidence suggested that this kind of impulsivity would be exacerbated in PD and under treatment by dopaminergic D2/3 receptor agonists. However, the mechanisms underlying ICDs in PD remain unknown and the respective contribution of dopamine lesion and treatment, combined with factors of vulnerability, remain to be determined. Moreover, waiting impulsivity, another form of behavioral inhibition which may lead to compulsive behaviors, has been poorly investigated in the framework of ICDs.In this thesis project, using a lesional rodent model of non-motor symptoms of PD, we addressed the question of whether denervation of the dopaminergic nigrostriatal system would promote the development of impulsivity when combined with dopamine agonist treatments. Rats were bilaterally injected in the SNc with the neurotoxin 6-OHDA to induce selective and partial denervation of the dorsal striatum. We then treated them with the dopamine D2/3 receptor agonist, pramipexole, a medication known to favor the development of ICDs in PD patients. Two different tasks were used to measure cognitive and motor impulsivity: the delay discounting task (DDT) and the 5-choice serial reaction time task (5-CSRTT) respectively. In the former, rats have to press a lever and choose between a smaller, but immediate reward and a larger, but delayed reward. For the latter, they have to wait for a stimulus light to come on. In the DDT, chronic administration of pramipexole treatment only increased impulsive choices in non-lesioned rats. Indeed, the dopaminergic lesion by itself, or in adjunction with the treatment, did not increase impulsivity. In the 5-CSRTT, pramipexole progressively increased premature responses, reflecting a pro-impulsive effect when the inter-trial interval is constant. However, when the interval was increased, pramipexole reduced the premature responses, exhibiting an anti-impulsive effect. Interestingly, this modulation of motor impulsivity was only observed in rats with a high level of impulsivity, suggesting that an impulsive endophenotype might be an important factor of vulnerability to the iatrogenic effects of pramipexole.The effect of this treatment was then investigated at a cellular level. It promotes overexpression of the dopamine D2 receptor mRNA within the striatum, and seems to alter glutamatergic synaptic connectivity suggested by electron microscopy. Moreover, we showed that the mammalian target of rapamycin complex 1 (mTORC1) pathway is lastingly over-activated in the nucleus accumbens, as already observed in drug addictions. In an attempt to make a causal link between this pathway and the behavioral changes, we treated rats with pramipexole and rapamycine, a specific inhibitor of this pathway. Surprisingly, this combination accentuated impulsivity even more, whereas rapamycine by itself did not promote impulsivity. This effect may be explained by the complexity of the kinetics of activation and inhibition of mTORC1 pathway.Taken together, these results suggest that impulsivity in PD may be triggered by an iatrogenic effect of the dopaminergic pramipexole treatment through an abnormal activation of the mTORC1 pathway within the nucleus accumbens.