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Del-Bel E, Padovan-Neto FE, Szawka RE, da-Silva CA, Raisman-Vozari R, Anselmo-Franci J, Romano-Dutra AC, Guimaraes FS. Counteraction by nitric oxide synthase inhibitor of neurochemical alterations of dopaminergic system in 6-OHDA-lesioned rats under L-DOPA treatment. Neurotox Res 2013; 25:33-44. [PMID: 23807548 DOI: 10.1007/s12640-013-9406-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 06/12/2013] [Accepted: 06/14/2013] [Indexed: 12/21/2022]
Abstract
Nitric oxide synthase inhibitors reduce L-3, (Del-Bel et al., Cell Mol Neurobiol 25(2):371-392, 2005) 4-dihydroxyphenylalanine (L-DOPA)-induced abnormal motor effects subsequent to depletion of dopaminergic neurons in rodents and non-human primates. The present study used quantitative high-performance liquid chromatography to analyze, for the first time, dopamine metabolism in striatum of rats in order to elucidate the mechanism of action of the nitric oxide synthase inhibitors. Adult male Wistar rats received unilateral microinjection of saline (sham) or 6-hydroxydopamine (6-OHDA-lesioned) in the medial forebrain bundle. Past 3 weeks, rats were treated during 21 days with L-DOPA/benserazide (30 mg/kg/7.5 mg/kg, respectively, daily). On the 22nd day rats received an intraperitoneal (i.p.) injection of either vehicle or 7-nitroindazole, a preferential neuronal nitric oxide synthase inhibitor before L-DOPA. Abnormal involuntary movements and rotarod test were assessed as behavioral correlate of motor responses. Lesion intensity was evaluated through tyrosine hydroxylase immunohystochemical reaction. Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and an extent of dopamine striatal tissue levels/dopamine metabolism were measured in the striatum. Lesion with 6-OHDA decreased dopamine, DOPAC, and DOPAC/dopamine ratio in the lesioned striatum. L-DOPA treatment induced abnormal involuntary movements and increased DOPAC/dopamine ratio (nearly five times) in the lesioned striatum. L-DOPA-induced dyskinesia was mitigated by 7-nitroindazole, which also decreased dopamine turnover, dopamine and DOPAC levels. Our results revealed an almost two times increase in dopamine content in the non-lesioned striatum of 6-OHDA-lesioned rats. Reduction of striatal DOPAC/dopamine ratio in dyskinetic rats may suggest an increase in the dopamine availability. Our data confirm contribution of nitrergic transmission in the pathogenesis of L-DOPA-induced dyskinesia with potential utilization of nitric oxide synthase inhibitors for treatment.
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Affiliation(s)
- Elaine Del-Bel
- Department of Morphology, Physiology and Pathology, School of Odontology, University of São Paulo, Campus Ribeirão Preto, Av. Café S/N, Ribeirão Preto, SP, 14040-904, Brazil,
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2
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Selective effects of dopamine depletion and L-DOPA therapy on learning-related firing dynamics of striatal neurons. J Neurosci 2013; 33:4782-95. [PMID: 23486949 DOI: 10.1523/jneurosci.3746-12.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Despite evidence that dopamine neurotransmission in the striatum is critical for learning as well as for movement control, little is yet known about how the learning-related dynamics of striatal activity are affected by dopamine depletion, a condition faced in Parkinson's disease. We made localized intrastriatal 6-hydroxydopamine lesions in rats and recorded within the dopamine-depleted sensorimotor striatal zone and its contralateral correspondent as the animals learned a conditional maze task. Rather than producing global, nonspecific elevations in firing rate across the task, the dopamine depletion altered striatal projection neuron activity and fast-spiking interneuron activity selectively, with sharply task-specific and cell type-specific effects, and often, with learning-stage selective effects as well. Striatal projection neurons with strong responses during the maze runs had especially elevated responsiveness during the maze runs. Projection neurons that, instead, fired most strongly before maze running showed elevated pre-start firing rates, but not during maze running, as learning progressed. The intrastriatal dopamine depletion severely affected the learning-related patterning of fast-spiking interneuron ensembles, especially during maze running and after extended training. Remarkably, L-DOPA treatment almost entirely reversed the depletion-induced elevations in pre-run firing of the projection neurons, and elevated their responses around start and end of maze runs. By contrast, L-DOPA failed to normalize fast-spiking interneuron activity. Thus the effects of striatal dopamine depletion and restoration on striatal activity are highly dependent not only on cell type, as previously shown, but also on the behavioral activity called for and the state of behavioral learning achieved.
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Ridderinkhof KR, van Wouwe NC, Band GPH, Wylie SA, Van der Stigchel S, van Hees P, Buitenweg J, van de Vijver I, van den Wildenberg WPM. A tribute to charlie chaplin: induced positive affect improves reward-based decision-learning in Parkinson's disease. Front Psychol 2012; 3:185. [PMID: 22707944 PMCID: PMC3374413 DOI: 10.3389/fpsyg.2012.00185] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 05/21/2012] [Indexed: 11/13/2022] Open
Abstract
Reward-based decision-learning refers to the process of learning to select those actions that lead to rewards while avoiding actions that lead to punishments. This process, known to rely on dopaminergic activity in striatal brain regions, is compromised in Parkinson’s disease (PD). We hypothesized that such decision-learning deficits are alleviated by induced positive affect, which is thought to incur transient boosts in midbrain and striatal dopaminergic activity. Computational measures of probabilistic reward-based decision-learning were determined for 51 patients diagnosed with PD. Previous work has shown these measures to rely on the nucleus caudatus (outcome evaluation during the early phases of learning) and the putamen (reward prediction during later phases of learning). We observed that induced positive affect facilitated learning, through its effects on reward prediction rather than outcome evaluation. Viewing a few minutes of comedy clips served to remedy dopamine-related problems associated with frontostriatal circuitry and, consequently, learning to predict which actions will yield reward.
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Affiliation(s)
- K Richard Ridderinkhof
- Department of Psychology, Amsterdam center for the study of adaptive control in brain and behavior (Acacia), University of Amsterdam Amsterdam, Netherlands
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Anzak A, Tan H, Pogosyan A, Djamshidian A, Ling H, Lees A, Brown P. Improvements in rate of development and magnitude of force with intense auditory stimuli in patients with Parkinson's disease. Eur J Neurosci 2011; 34:124-32. [PMID: 21645135 DOI: 10.1111/j.1460-9568.2011.07735.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Patients with Parkinson's disease can show brief but dramatic normalization of motor activity in highly arousing situations, a phenomenon often termed paradoxical kinesis. We sought to mimic this in a controlled experimental environment. Nine patients with Parkinson's disease and nine age-matched healthy controls were asked to grip a force dynamometer as quickly and strongly as possible in response to a visual cue. A loud (96 dB) auditory stimulus was delivered at the same time as the visual cue in ~50% of randomly selected trials. In patients with Parkinson's disease, the experiment was conducted after overnight withdrawal of antiparkinsonian drugs and again 1 h after patients had taken their usual morning medication. Patients showed improvements in the peak rate of force development and the magnitude of force developed when loud auditory stimuli accompanied visual cues. Equally, they showed improvements in the times taken to reach the peak rate of force development and their maximal force. The paradoxical facilitatory effect of sound was similar whether patients were off or on their usual antiparkinsonian medication, and could be reproduced in age-matched healthy controls. We conclude that motor improvement induced by loud auditory stimuli in Parkinson's disease is related to a physiological phenomenon which survives both with and after withdrawal of antiparkinsonian medication. The potential independence of the mediating pathways from the dopaminergic system provides impetus for further investigation as it may yield a novel nondopaminergic target for therapeutic manipulation in Parkinson's disease.
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Affiliation(s)
- Anam Anzak
- Sobell Department of Motor Neuroscience and Movement Disorders, Queen Square, London, UK
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5
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Xu D, Karain B, Brantley E, Shi WX. Effects of L-DOPA on nigral dopamine neurons and local field potential: comparison with apomorphine and muscimol. J Pharmacol Exp Ther 2011; 337:533-9. [PMID: 21330359 DOI: 10.1124/jpet.110.177816] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
L-DOPA is more effective than direct dopamine (DA) agonists in relieving the motor deficits in Parkinson's disease. Using in vivo recording, we compared the effect of l-DOPA and the direct DA agonist apomorphine on DA neurons in rat substantia nigra (SN). L-DOPA (50-100 mg/kg i.v.) decreased the firing rate as well as the variability and slow oscillation (SO) of firing. All effects were blocked by raclopride and mimicked by quinpirole, suggesting that they are mediated through D2-like receptors. Autoreceptor-selective doses of apomorphine (5-20 μg/kg i.v.) also inhibited all three parameters. The magnitude of the inhibition, however, was significantly greater than that induced by L-DOPA. Neither L-DOPA nor apomorphine had a consistent effect on SN local field potentials (LFPs). The GABA agonist muscimol, known to preferentially inhibit SN non-DA neurons, consistently inhibited the SO in both DA cell firing and LFPs. These results suggest that SN LFPs mainly reflect the synaptic potentials in non-DA neurons, and L-DOPA and apomorphine, unlike muscimol, affect DA neurons primarily through DA autoreceptors. DA autoreceptor activation is known to hyperpolarize DA cells by increasing the membrane conductance to K(+). This increase in membrane conductance would shunt synaptic input to DA neurons, thereby decreasing the variability and SO in DA cell firing. The low potency of L-DOPA to inhibit DA cell firing and reduce their responses to synaptic input may partially account for its superior therapeutic efficacy in Parkinson's disease compared with apomorphine and other direct DA agonists.
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Affiliation(s)
- Dan Xu
- Department of Pharmaceutical Sciences, Loma Linda University School of Pharmacy, 11175 Campus St., Loma Linda, CA 92350, USA
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6
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Frank MJ, Fossella JA. Neurogenetics and pharmacology of learning, motivation, and cognition. Neuropsychopharmacology 2011; 36:133-52. [PMID: 20631684 PMCID: PMC3055524 DOI: 10.1038/npp.2010.96] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 06/09/2010] [Accepted: 06/10/2010] [Indexed: 02/07/2023]
Abstract
Many of the individual differences in cognition, motivation, and learning-and the disruption of these processes in neurological conditions-are influenced by genetic factors. We provide an integrative synthesis across human and animal studies, focusing on a recent spate of evidence implicating a role for genes controlling dopaminergic function in frontostriatal circuitry, including COMT, DARPP-32, DAT1, DRD2, and DRD4. These genetic effects are interpreted within theoretical frameworks developed in the context of the broader cognitive and computational neuroscience literature, constrained by data from pharmacological, neuroimaging, electrophysiological, and patient studies. In this framework, genes modulate the efficacy of particular neural computations, and effects of genetic variation are revealed by assays designed to be maximally sensitive to these computations. We discuss the merits and caveats of this approach and outline a number of novel candidate genes of interest for future study.
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Affiliation(s)
- Michael J Frank
- Department of Cognitive, Linguistic and Psychological Sciences, Brown Institute for Brain Science, Brown University, Providence, RI 02912-1978, USA.
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Wiecki TV, Frank MJ. Neurocomputational models of motor and cognitive deficits in Parkinson's disease. PROGRESS IN BRAIN RESEARCH 2010; 183:275-97. [PMID: 20696325 DOI: 10.1016/s0079-6123(10)83014-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We review the contributions of biologically constrained computational models to our understanding of motor and cognitive deficits in Parkinson's disease (PD). The loss of dopaminergic neurons innervating the striatum in PD, and the well-established role of dopamine (DA) in reinforcement learning (RL), enable neural network models of the basal ganglia (BG) to derive concrete and testable predictions. We focus in this review on one simple underlying principle - the notion that reduced DA increases activity and causes long-term potentiation in the indirect pathway of the BG. We show how this theory can provide a unified account of diverse and seemingly unrelated phenomena in PD including progressive motor degeneration as well as cognitive deficits in RL, decision making and working memory. DA replacement therapy and deep brain stimulation can alleviate some aspects of these impairments, but can actually introduce negative effects such as motor dyskinesias and cognitive impulsivity. We discuss these treatment effects in terms of modulation of specific mechanisms within the computational framework. In addition, we review neurocomputational interpretations of increased impulsivity in the face of response conflict in patients with deep-brain-stimulation.
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Dopaminergic drugs modulate learning rates and perseveration in Parkinson's patients in a dynamic foraging task. J Neurosci 2009; 29:15104-14. [PMID: 19955362 DOI: 10.1523/jneurosci.3524-09.2009] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Making appropriate choices often requires the ability to learn the value of available options from experience. Parkinson's disease is characterized by a loss of dopamine neurons in the substantia nigra, neurons hypothesized to play a role in reinforcement learning. Although previous studies have shown that Parkinson's patients are impaired in tasks involving learning from feedback, they have not directly tested the widely held hypothesis that dopamine neuron activity specifically encodes the reward prediction error signal used in reinforcement learning models. To test a key prediction of this hypothesis, we fit choice behavior from a dynamic foraging task with reinforcement learning models and show that treatment with dopaminergic drugs alters choice behavior in a manner consistent with the theory. More specifically, we found that dopaminergic drugs selectively modulate learning from positive outcomes. We observed no effect of dopaminergic drugs on learning from negative outcomes. We also found a novel dopamine-dependent effect on decision making that is not accounted for by reinforcement learning models: perseveration in choice, independent of reward history, increases with Parkinson's disease and decreases with dopamine therapy.
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Cohen MX, Frank MJ. Neurocomputational models of basal ganglia function in learning, memory and choice. Behav Brain Res 2008; 199:141-56. [PMID: 18950662 DOI: 10.1016/j.bbr.2008.09.029] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 09/24/2008] [Accepted: 09/24/2008] [Indexed: 11/24/2022]
Abstract
The basal ganglia (BG) are critical for the coordination of several motor, cognitive, and emotional functions and become dysfunctional in several pathological states ranging from Parkinson's disease to Schizophrenia. Here we review principles developed within a neurocomputational framework of BG and related circuitry which provide insights into their functional roles in behavior. We focus on two classes of models: those that incorporate aspects of biological realism and constrained by functional principles, and more abstract mathematical models focusing on the higher level computational goals of the BG. While the former are arguably more "realistic", the latter have a complementary advantage in being able to describe functional principles of how the system works in a relatively simple set of equations, but are less suited to making specific hypotheses about the roles of specific nuclei and neurophysiological processes. We review the basic architecture and assumptions of these models, their relevance to our understanding of the neurobiological and cognitive functions of the BG, and provide an update on the potential roles of biological details not explicitly incorporated in existing models. Empirical studies ranging from those in transgenic mice to dopaminergic manipulation, deep brain stimulation, and genetics in humans largely support model predictions and provide the basis for further refinement. Finally, we discuss possible future directions and possible ways to integrate different types of models.
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Affiliation(s)
- Michael X Cohen
- Department of Psychology, Program in Neuroscience, University of Arizona, 1503 E University Blvd, Tucson, AZ 85721, United States
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The l-amino acid carrier inhibitor 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH) reduces l-dopa-elicited responses in dopaminergic neurons of the substantia nigra pars compacta. Exp Neurol 2008; 212:230-3. [DOI: 10.1016/j.expneurol.2008.04.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 03/03/2008] [Accepted: 04/01/2008] [Indexed: 11/23/2022]
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Metz GA, Farr T, Ballermann M, Whishaw IQ. Chronic levodopa therapy does not improve skilled reach accuracy or reach range on a pasta matrix reaching task in 6-OHDA dopamine-depleted (hemi-Parkinson analogue) rats. Eur J Neurosci 2001; 14:27-37. [PMID: 11488946 DOI: 10.1046/j.0953-816x.2001.01615.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
L-dopa therapy reverses some but not all of the motor deficits in human Parkinson patients. Although a number rat analogues of human Parkinson's disease have been developed for evaluating the efficacy of drug therapies, it is not known whether L-dopa has a similar selective action on the motor symptoms in the rat models. To examine the effectiveness of L-dopa in reversing the motor deficits in rats, we administered 6-OHDA unilaterally to produce hemi-Parkinson rats, which were then trained to reach for food using either their impaired (contralateral to the lesion) limb or their good (ipsilateral to the lesion) limb. To assess the skill, accuracy and range of limb movement, rats reached for pasta from a horizontal array of 260 vertically orientated pieces of pasta. The number and location of pasta pieces taken from this matrix was calculated and the qualitative aspects of the reaching movements were rated. The quantitative data on pasta sticks retrieved indicated that forelimb extension and movement radius around the shoulder joint was reduced by 6-OHDA treatment and did not improve after chronic L-dopa treatment. The qualitative analysis showed that grasping patterns, paw movements and body movements impaired by the lesion were also not improved by L-dopa treatment. These findings are the first in the rat to suggest that whereas L-dopa has a general activating effect on the rat's whole-body movements, as displayed in contralateral rotation, its effectiveness does not extend to skilled forelimb movements. The results are discussed in relationship to the idea that the restoration of some skilled movements may require normal synaptic function.
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Affiliation(s)
- G A Metz
- Department of Psychology and Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, AB, Canada, T1K 3M4.
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Garris PA, Walker QD, Wightman RM. Dopamine release and uptake rates both decrease in the partially denervated striatum in proportion to the loss of dopamine terminals. Brain Res 1997; 753:225-34. [PMID: 9125407 DOI: 10.1016/s0006-8993(97)00003-6] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The present study tested the hypothesis that normal concentrations of extracellular dopamine are preserved in the partially denervated striatum without active compensatory changes in dopamine uptake or release. One to four weeks after adult rats were unilaterally lesioned with 6-hydroxydopamine, fast-scan cyclic voltammetry at Nafion-coated, carbon-fiber microelectrodes was used to monitor extracellular dopamine levels in vivo, under urethane anesthesia. Simultaneous voltammetric recordings were collected in the lesioned and contralateral control striata. Extracellular dopamine was elicited by bilateral electrical stimulation of the medial forebrain bundle. A 20 Hz stimulation evoked similar concentrations of extracellular dopamine in both lesioned and control striata, although tissue dopamine was decreased 30-70% in lesioned striata, as determined subsequently by HPLC-EC. However, kinetic analysis of the voltammetric recordings revealed that the concentration of dopamine released per stimulus pulse and Vmax for dopamine uptake decreased in proportion to the magnitude of the lesion. These data support the hypothesis that normal extracellular dopamine levels can be generated in the partially lesioned striatum in the absence of active neuronal compensation. These results also suggest that passive mechanisms involved in the regulation of extracellular dopamine play an important role in maintaining function during the preclinical or presymptomatic phase of Parkinson's disease.
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Affiliation(s)
- P A Garris
- Department of Biological Sciences, Illinois State University, Normal 61790-4120, USA
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14
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Grace AA. The tonic/phasic model of dopamine system regulation: its relevance for understanding how stimulant abuse can alter basal ganglia function. Drug Alcohol Depend 1995; 37:111-29. [PMID: 7758401 DOI: 10.1016/0376-8716(94)01066-t] [Citation(s) in RCA: 193] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The changes in dopamine system regulation occurring during stimulant administration are examined in relation to a new model of dopamine system function. This model is based on the presence of a tonic low level of extracellular dopamine that is released by the presynaptic action of corticostriatal afferents. In contrast, spike-dependent dopamine release results in a phasic, high concentration of dopamine in the synaptic cleft that is rapidly inactivated by reuptake. Tonic dopamine has the ability to down-modulate spike-dependent phasic dopamine release via stimulation of the very sensitive dopamine autoreceptors present on dopamine terminals. Stimulants are known to elicit locomotion and stimulate reward sites by releasing dopamine from terminals in the nucleus accumbens, which is followed by a rebound depression. It is proposed that the initial activating action of stimulants is caused by increasing the release of dopamine into the synaptic cleft to activate the phasic dopamine response. However, by interfering with dopamine uptake, stimulants also allow dopamine to escape the synaptic cleft, thereby depressing subsequent spike-dependent phasic dopamine release by increasing the tonic stimulation of the autoreceptor. In contrast, repeated stimulant administration is proposed to cause long-term sensitization by pharmacological disruption of a cascade of homeostatic compensatory processes. Upon drug withdrawal, the fast compensatory systems that were blocked by stimulants rapidly restore homeostasis to the system at a new steady-state level of interaction. As a consequence, the slowly changing but potentially more destabilizing compensatory responses are prevented from returning to their baseline conditions. This results in a permanent change in the responsivity of the system. Homeostatic systems are geared to compensate for unidimensional alterations in a system, and are capable of restoring function even after massive brain lesions or the continuous presence of stimulant drugs. However, the system did not evolve to deal effectively with repetitive introduction and withdrawal of drugs that disrupt dopamine system regulation. As a consequence, repeated insults to a biological system by application and withdrawal of drugs that interfere with its homeostatic regulation may be capable of inducing non-reversible changes in its response to exogenous and endogenous stimuli.
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Affiliation(s)
- A A Grace
- Department of Neuroscience, University of Pittsburgh, PA 15260, USA
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Robinson TE, Noordhoorn M, Chan EM, Mocsary Z, Camp DM, Whishaw IQ. Relationship between asymmetries in striatal dopamine release and the direction of amphetamine-induced rotation during the first week following a unilateral 6-OHDA lesion of the substantia nigra. Synapse 1994; 17:16-25. [PMID: 8042143 DOI: 10.1002/syn.890170103] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In animals with a large unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal dopamine (DA) system the traditional "rotational behavior model" states that amphetamine will induce circling behavior towards the denervated striatum (ipsiversive), that is, away from the side where there is greater amphetamine-stimulated DA release and greater DA receptor stimulation. It is puzzling, therefore, why amphetamine induces contraversive rotation in rats tested 4 days after a unilateral 6-OHDA lesion, despite a 90-95% loss of the dopaminergic input to the striatum by this time. Rats reverse their direction of amphetamine-induced rotation by 8 days post-lesion and turn in the ipsiversive direction thereafter. To try and resolve this paradox, bilateral striatal microdialysis was used to estimate the effects of amphetamine on DA neurotransmission on Day 4 and Day 8 following a large unilateral 6-OHDA lesion of the substantia nigra. On Day 4 post-lesion, amphetamine produced a moderate (around 50% of control) increase in the extracellular concentration of DA in the denervated striatum. This amphetamine-releasable pool of DA was exhausted by a single amphetamine-challenge, because a second injection of amphetamine given 3 h after the first did not produce a comparable increase in DA. It is suggested that on Day 4 post-lesion the amount of DA released by amphetamine in the denervated striatum is sufficient to produce greater DA receptor stimulation on that side, because of DA receptor supersensitivity, and this leads to contraversive rotation. On Day 8 post-lesion, amphetamine induced DA release in the intact striatum but had no effect on extracellular DA in the denervated striatum (DA was nondetectable). On Day 8, therefore, DA receptor stimulation would be greatest in the intact striatum, leading to ipsiversive rotation. In conclusion, it is suggested that the seemingly paradoxical reversal in the direction of amphetamine-induced rotation that occurs over the first week following a unilateral 6-OHDA lesion is consistent with the traditional rotational model, and is due to time-dependent changes in the ability of amphetamine to release DA in the denervated striatum.
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Affiliation(s)
- T E Robinson
- Department of Psychology, University of Michigan, Ann Arbor 48104-1687
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Cass WA, Zahniser NR, Flach KA, Gerhardt GA. Clearance of exogenous dopamine in rat dorsal striatum and nucleus accumbens: role of metabolism and effects of locally applied uptake inhibitors. J Neurochem 1993; 61:2269-78. [PMID: 8245977 DOI: 10.1111/j.1471-4159.1993.tb07469.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In vivo electrochemistry was used to investigate the mechanisms contributing to the clearance of locally applied dopamine in the dorsal striatum and nucleus accumbens of urethane-anesthetized rats. Chronoamperometric recordings were continuously made at 5 Hz using Nafion-coated carbon fiber electrodes. When a finite amount of dopamine was pressure-ejected at 5-min intervals from a micropipette adjacent to the electrode, transient and reproducible dopamine signals were detected. Substitution of L-alpha-methyldopamine, a substrate for the dopamine transporter but not for monoamine oxidase, for dopamine in the micropipette did not substantially alter the time course of the resulting signals. This indicates that metabolism of locally applied dopamine to 3,4-dihydroxy-phenylacetic acid is not responsible for the decline in the dopamine signal. Similarly, changing the applied oxidation potential from +0.45 to +0.80 V, which allows for detection of 3-methoxytyramine formed from dopamine via catechol-O-methyltransferase, had little effect on signal amplitude or time course. In contrast, lesioning the dopamine terminals with 6-hydroxydopamine, or locally applying the dopamine uptake inhibitors cocaine or nomifensine before pressure ejection of dopamine, significantly increased the amplitude and time course of the dopamine signals in both regions. The effects of cocaine and nomifensine were greater in the nucleus accumbens than in the dorsal striatum. Local application of lidocaine and procaine had no effect on the dopamine signals. Initial attempts at modeling resulted in curves that were in qualitative agreement with our experimental findings. Taken together, these data indicate that (1) uptake of dopamine by the neuronal dopamine transporter, rather than metabolism or diffusion, is the major mechanism for clearing locally applied dopamine from the extracellular milieu of the dorsal striatum and nucleus accumbens, and (2) the nucleus accumbens is more sensitive to the effects of inhibitors of dopamine uptake than is the dorsal striatum.
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Affiliation(s)
- W A Cass
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262
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17
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Grace AA. Cortical regulation of subcortical dopamine systems and its possible relevance to schizophrenia. J Neural Transm (Vienna) 1993; 91:111-34. [PMID: 8099795 DOI: 10.1007/bf01245228] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A unique model of DA system regulation is presented, in which tonic steady-state DA levels in the ECF act to down-regulate the response of the system to pulsatile DA released by DA cell action potential generation. This type of regulation is similar in many respects to the phenomenon proposed to mediate the action of norepinephrine on target neurons; i.e., an increase in the "signal-to-noise" ratio as measured by postsynaptic cell firing (Freedman et al., 1977; Woodward et al., 1979). However, in this model the signal and the noise are neurochemical rather than electrophysiological. Furthermore, the "noise" (tonic DA in the ECF) actually down-regulates the "signal" (phasic DA release) directly, and thereby provides a "signal" of its own that affects the system over a longer time-course. Therefore, the difference between signal and noise may also depend on the time frame under which such determinations are made.
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Affiliation(s)
- A A Grace
- Department of Behavioral Neuroscience, University of Pittsburgh, PA
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Grace AA. The depolarization block hypothesis of neuroleptic action: implications for the etiology and treatment of schizophrenia. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1992; 36:91-131. [PMID: 1356143 DOI: 10.1007/978-3-7091-9211-5_6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
Antipsychotic drugs are known to block dopamine receptors soon after their administration, resulting in an increase in dopamine neuron firing and dopamine turnover. Nonetheless, antipsychotic drugs must be administered repeatedly to schizophrenics before therapeutic benefits are produced. Recordings from dopamine neurons in rats have revealed that chronic antipsychotic drug treatment results in the time-dependent inactivation of dopamine neuron firing via over-excitation, or depolarization block. Furthermore, the clinical profile of the response to antipsychotic drugs appears to correspond to the dopamine system affected: antipsychotic drugs that exert therapeutic actions in schizophrenics inactivate dopamine neuron firing in the limbic-related ventral tegmental area, whereas drugs that precipitate extrapyramidal side effects cause depolarization block of the motor-related substantia nigra dopamine cells. One factor that remains unresolved with regard to the actions of antipsychotic drugs is the relationship between dopamine turnover and depolarization block--i.e., why does a significant level of dopamine release or turnover remain after antipsychotic drug treatment if dopamine cells are no longer firing? We addressed this question using an acute model of neuroleptic-induced depolarization block. In this model, dopamine cells recorded in rats one month after partial dopamine lesions could be driven into depolarization block by the acute administration of moderate doses of haloperidol. However, similar doses of haloperidol, which were effective at increasing dopamine levels in the striatum of intact rats, failed to change dopamine levels in lesioned rats. This is consistent with a model in which neuroleptic drugs exert their therapeutic effects in schizophrenics by causing depolarization block in DA cells, thereby preventing further activation of dopamine neuron firing in response to external stimuli. Thus, attenuating the responsivity of the dopamine system to stimuli may be more relevant to the therapeutic actions of antipsychotic drugs than receptor blockade or decreases in absolute levels of dopamine, which could presumably be circumvented by homeostatic adaptations in this highly plastic system.
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Affiliation(s)
- A A Grace
- Department of Behavioral Neuroscience, University of Pittsburgh, PA
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19
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Zigmond MJ, Hastings TG, Abercrombie ED. Neurochemical responses to 6-hydroxydopamine and L-dopa therapy: implications for Parkinson's disease. Ann N Y Acad Sci 1992; 648:71-86. [PMID: 1637074 DOI: 10.1111/j.1749-6632.1992.tb24525.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- M J Zigmond
- Department of Behavioral Neuroscience, University of Pittsburgh, Pennsylvania 15260
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20
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Martin C, Meissl H. Effects of dopaminergic and noradrenergic mechanisms on the neuronal activity of the isolated pineal organ of the trout, Oncorhynchus mykiss. J Neural Transm (Vienna) 1992; 88:37-51. [PMID: 1575952 DOI: 10.1007/bf01245035] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effects of exogenous applied catecholamines on the neuronal activity of ganglion cells of the luminance type (achromatic cells) were investigated in the photosensitive pineal organ of the trout, Oncorhynchus mykiss. Extracellular recordings were performed on neurons of the superfused isolated pineal organ. Addition of dopamine to the superfusion medium increased the spontaneous activity of more than 60% of the achromatic neurons (n = 25). The D1-dopamine antagonist SCH-23390 and D2-dopamine antagonist spiperone reversed the dopamine-induced stimulation of ganglion cells and inhibited their maintained activity, which suggests that dopamine acts via both D1- and D2-receptors. Norepinephrine, the beta-adrenergic agonist isoproterenol, and DOPA enhanced the spontaneous activity of most of the ganglion cells, whereas the beta-antagonist propranolol depressed the discharge rate and reversed the action of isoproterenol. This suggests that catecholamines might play a modulatory role in the regulation of the neural activity of pineal luminance neurons.
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Affiliation(s)
- C Martin
- Max-Planck-Institute for Physiological and Clinical Research, W. G. Kerckhoff-Institute, Bad Nauheim, Federal Republic of Germany
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21
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Koshimura K, Ohue T, Akiyama Y, Itoh A, Miwa S. L-dopa administration enhances exocytotic dopamine release in vivo in the rat striatum. Life Sci 1992; 51:747-55. [PMID: 1325018 DOI: 10.1016/0024-3205(92)90484-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Peripheral administration of L-3,4-dihydroxyphenylalanine (L-DOPA) methylester increased extracellular levels of DOPA and dopamine (DA) in the rat striatum monitored by in vivo brain microdialysis. The increase in DA levels persisted after inhibition of DA reuptake by nomifensine. Administration of blockers of voltage-dependent Na+ (tetrodotoxin) or Ca2+ (NKY-722) channels through the dialysis membrane completely eliminated the increase in DA levels. These results demonstrate that the L-DOPA-induced DA release is exocytotic in nature and hence, derived from neurons in the striatum.
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Affiliation(s)
- K Koshimura
- Department of Pharmacology, Kyoto University Faculty of Medicine, Japan
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22
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Aceves J, Floran B, Martinez-Fong D, Sierra A, Hernandez S, Mariscal S. L-dopa stimulates the release of [3H]gamma-aminobutyric acid in the basal ganglia of 6-hydroxydopamine lesioned rats. Neurosci Lett 1991; 121:223-6. [PMID: 1902287 DOI: 10.1016/0304-3940(91)90690-u] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
L-DOPA stimulated the K(+)-induced [3H]GABA (gamma-aminobutyric acid) release from slices of substantia nigra pars reticulata, entopeduncular nucleus, globus pallidus and caudate-putamen isolated from the ipsilateral side of 6-hydroxydopamine-lesioned rats, but the release from ipsilateral subthalamic slices was not affected. In substantia nigra, L-DOPA stimulation (EC50 = 1 microM) of [3H]GABA release was dose-dependently blocked (IC50 = 0.1 microM for the stimulation caused by 10 microM L-DOPA) by the D1 antagonist SCH 23390, but was not affected by (-)-sulpiride, a D2 antagonist. SCH 23390 also blocked the stimulation in the other nuclei. The DOPA decarboxylase inhibitor NSD-1015 (500 microM) did not prevent the stimulation induced by L-DOPA in all of the studied nuclei. The results suggest that L-DOPA is able to activate D1 receptors located on the terminals of striatal projections via the dopamine formed by a decarboxylation mediated by an NSD-1015-resistant enzyme. Activation of the presynaptic D1 receptors results in stimulation of GABA release.
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Affiliation(s)
- J Aceves
- Department of Physiology, Biophysics and Neurosciences, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Mexico D.F
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23
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Grace AA. Phasic versus tonic dopamine release and the modulation of dopamine system responsivity: a hypothesis for the etiology of schizophrenia. Neuroscience 1991; 41:1-24. [PMID: 1676137 DOI: 10.1016/0306-4522(91)90196-u] [Citation(s) in RCA: 1211] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A novel mechanism for regulating dopamine activity in subcortical sites and its possible relevance to schizophrenia is proposed. This hypothesis is based on the regulation of dopamine release into subcortical regions occurring via two independent mechanisms: (1) transient or phasic dopamine release caused by dopamine neuron firing, and (2) sustained, "background" tonic dopamine release regulated by prefrontal cortical afferents. Behaviorally relevant stimuli are proposed to cause short-term activation of dopamine cell firing to trigger the phasic component of dopamine release. In contrast, tonic dopamine release is proposed to regulate the intensity of the phasic dopamine response through its effect on extracellular dopamine levels. In this way, tonic dopamine release would set the background level of dopamine receptor stimulation (both autoreceptor and postsynaptic) and, through homeostatic mechanisms, the responsivity of the system to dopamine in these sites. In schizophrenics, a prolonged decrease in prefrontal cortical activity is proposed to reduce tonic dopamine release. Over time, this would elicit homeostatic compensations that would increase overall dopamine responsivity and thereby cause subsequent phasic dopamine release to elicit abnormally large responses.
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Affiliation(s)
- A A Grace
- Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260
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24
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Abercrombie ED, Bonatz AE, Zigmond MJ. Effects of L-dopa on extracellular dopamine in striatum of normal and 6-hydroxydopamine-treated rats. Brain Res 1990; 525:36-44. [PMID: 2123121 DOI: 10.1016/0006-8993(90)91318-b] [Citation(s) in RCA: 281] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In vivo microdialysis was used to examine the effect of L-3,4-dihydroxyphenylalanine (L-DOPA) administration upon dopamine (DA) in extracellular fluid both in intact striatum and in striatum of rats treated with the catecholaminergic neurotoxin 6-hydroxydopamine (6-HDA). Basal extracellular levels of DA were not significantly altered by 6-HDA unless the DA content of striatal tissue was reduced to less than 20% of control. Peripheral aromatic amino acid decarboxylase (AADC) inhibition (RO4-4602, 50 mg/kg i.p.) followed by L-DOPA treatment (100 mg/kg i.p.) elevated extracellular DA in striatum of control rats from 37 +/- 5 to 68 +/- 11 pg/sample (n = 7; values corrected for recovery of the dialysis probe). In animals with severe bilateral depletions of DA in striatal tissue (mean depletion 87%; n = 6), L-DOPA increased extracellular DA in striatum from 8 +/- 3 to 266 +/- 60 pg/sample. In animals with large unilateral depletions of DA in striatal tissue (mean depletion 96%; n = 6), the increase in extracellular DA in striatum after L-DOPA was greater on the lesion side (from 7 +/- 4 to 245 +/- 67 pg/sample) than on the intact side (from 28 +/- 11 to 61 +/- 8 pg/sample). Animals with unilateral DA depletions showed contralateral circling behavior after L-DOPA. Increases in extracellular DA approaching the magnitude of those occurring in DA-depleted striata were observed when intact animals were treated with nomifensine (5 mg/kg i.p.; n = 5), an inhibitor of high-affinity DA uptake, in addition to L-DOPA.
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Affiliation(s)
- E D Abercrombie
- Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260
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25
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Wightman RM, Zimmerman JB. Control of dopamine extracellular concentration in rat striatum by impulse flow and uptake. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1990; 15:135-44. [PMID: 2282449 DOI: 10.1016/0165-0173(90)90015-g] [Citation(s) in RCA: 247] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Advances in measurement techniques have enabled the extracellular concentration of dopamine to be monitored inside striatal structures during transient electrical stimulation of the medial forebrain bundle. The observed concentration changes can be accounted for by a mathematical model as a function of the frequency employed and the stimulus duration. Overflow curves can be described by 3 kinetic parameters: the concentration of dopamine released per stimulus pulse, and the Km and Vmax of uptake. In terms of this model, the kinetics of overflow during stimulation is found to be identical in the nucleus accumbens and caudate nucleus with the exception that the Vmax for uptake is lower in the former region. Maximal uptake is also found to be lower in animals with partial lesions of dopamine neurons. Measured concentrations vary with stimulation frequency from 10 to 60 Hz in a manner that can be predicted by the model. Competitive uptake inhibitors have their primary effect on overflow in the limit of low stimulus frequencies. In contrast, D2 antagonists, which increase the concentration of dopamine released per stimulus pulse, have a moderate effect in low and high frequency ranges, but cause a significant maximal increase in extracellular dopamine concentrations at a mid-range frequency. Both calculated response and experimental findings indicate that in the caudate nucleus, the upper frequency for observable uptake inhibition and the characteristic maximum frequency for the receptor-mediated response occur at higher values than in the nucleus accumbens. The model appears to be useful for predicting dopamine extracellular concentrations over a wide range of conditions, and its predictions may be valid when extended to more physiological situations.
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Affiliation(s)
- R M Wightman
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290
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26
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Abstract
We have examined the effects of L-dihydroxyphenylalanine (L-DOPA) on endogenous dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) efflux from superfused striatal slices prepared from adult male rats. Superfusion with L-DOPA (10 microM) caused a modest elevation in the tissue levels of DA and greatly increased the basal efflux and stimulation-evoked overflow of DA. Stimulation of slices under Ca2(+)-free conditions abolished DA overflow occurring in the absence of L-DOPA, but reduced DA overflow in the presence of L-DOPA by only 56%. Ca2(+)-independent DA release was not reduced by nomifensine. Destruction of DA terminals by pretreatment with 6-hydroxydopamine did not alter the capacity of L-DOPA to elevate tissue DA content. However, it attenuated the impact of L-DOPA on DA efflux, although this effect was somewhat smaller than was the apparent loss of DA terminals. These results suggest the following conclusions: (1) L-DOPA increases both the spontaneous and depolarization-induced release of DA; (2) some of the DA formed from L-DOPA can be released in response to depolarization by a process that does not involve either Ca2(+)-dependent exocytosis or reverse transport; and (3) most but not all of the DA efflux occurring in the presence of L-DOPA represents DA released from DA terminals. Furthermore, the observations suggest that the loss of DA terminals due to the progression of Parkinson's disease may be importantly involved in the gradual loss of clinical efficacy of the drug during chronic treatment.
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Affiliation(s)
- G L Snyder
- Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260
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27
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Zigmond MJ, Abercrombie ED, Stricker EM. Partial damage to nigrostriatal bundle: compensatory changes and the action of L-dopa. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1990; 29:217-32. [PMID: 2193107 DOI: 10.1007/978-3-7091-9050-0_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Parkinson's disease is associated with degeneration of the nigrostriatal bundle. However, the neurological symptoms that accompany this disease do not emerge until the degenerative process is almost complete. Early studies with animals models suggested that the extensive preclinical phase of Parkinsonism was due in part to the development of a compensatory hyperactivity within remaining dopamine-containing neurons. Other studies suggested that systemic administration of L-DOPA could reduce the neurological symptoms once they emerged by further increasing the availability of dopamine in striatum. Subsequent work has supported both hypothesis.
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Affiliation(s)
- M J Zigmond
- Department of Behavioral Neuroscience, University of Pittsburgh, PA
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28
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Dluzen DE, Ramirez VD. Progesterone enhances L-dopa-stimulated dopamine release from the caudate nucleus of freely behaving ovariectomized-estrogen-primed rats. Brain Res 1989; 494:122-8. [PMID: 2765910 DOI: 10.1016/0006-8993(89)90150-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In the present experiment we examined the effect of progesterone upon dopamine (DA) release induced by a direct infusion of unlabeled L-dihydroxyphenylalanine (L-DOPA) into the caudate nucleus of freely behaving rats. Ovariectomized rats were implanted with a push-pull cannula directed at the caudate nucleus and subjected to perfusion under 3 different hormonal conditions: (1) following 4 days of treatment with estradiol benzoate (EB), (2) following 4 days of treatment with estradiol benzoate plus progesterone at 4-6 h prior to perfusion (EB + P-4-6 h) and (3) following 4 days of treatment with estradiol benzoate plus progesterone at 28 h prior to perfusion (EB + P-28 h). During each perfusion session and under each of the 3 hormonal treatment conditions, L-DOPA was infused through the push side of the cannula. Three increasing doses of L-DOPA (10(-6), 10(-5) and 10(-4) M) were infused with a 45-75 min interval between infusions. Regardless of hormonal treatment condition, a clear dose-response increase in DA and 3,4-dihydroxyphenylacetic acid (DOPAC), but not 5-HIAA, output was observed in response to the increasing doses of L-DOPA infusion. For each of the 3 doses of L-DOPA, maximal DA output was observed for animals tested under the EB + P-4-6 h hormonal condition, with statistically significant differences in the areas under the L-DOPA-stimulated DA response curves obtained following the 10(-6) and 10(-5) M doses of L-DOPA infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D E Dluzen
- Department of Physiology and Biophysics, University of Illinois, Urbana 61801
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