sch-23390 and Parkinsonian-Disorders

The loss of dopamine (DA) in Parkinson's is accompanied by the emergence of exaggerated theta and beta frequency neuronal oscillatory activity in the primary motor cortex (M1) and basal ganglia. DA replacement therapy or deep brain stimulation reduces the power of these oscillations and this is coincident with an improvement in motor performance implying a causal relationship. Here we provide in vitro evidence for the differential modulation of theta and gamma activity in M1 by DA acting at receptors exhibiting conventional and non-conventional DA pharmacology. Recording local field potentials in deep layer V of rat M1, co-application of carbachol (CCh, 5 μM) and kainic acid (KA, 150 nM) elicited simultaneous oscillations at a frequency of 6.49 ± 0.18 Hz (theta, n = 84) and 34.97 ± 0.39 Hz (gamma, n = 84). Bath application of DA resulted in a decrease in gamma power with no change in theta power. However, application of either the D1-like receptor agonist SKF38393 or the D2-like agonist quinpirole increased the power of both theta and gamma suggesting that the DA-mediated inhibition of oscillatory power is by action at other sites other than classical DA receptors. Application of amphetamine, which promotes endogenous amine neurotransmitter release, or the adrenergic α1-selective agonist phenylephrine mimicked the action of DA and reduced gamma power, a result unaffected by prior co-application of D1 and D2 receptor antagonists SCH23390 and sulpiride. Finally, application of the α1-adrenergic receptor antagonist prazosin blocked the action of DA on gamma power suggestive of interaction between α1 and DA receptors. These results show that DA mediates complex actions acting at dopamine D1-like and D2-like receptors, α1 adrenergic receptors and possibly DA/α1 heteromultimeric receptors to differentially modulate theta and gamma activity in M1.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Adrenergic alpha-1 Receptor Agonists; Adrenergic alpha-1 Receptor Antagonists; Animals; Benzazepines; Dopamine; Dopamine Agonists; Dopamine D2 Receptor Antagonists; Male; Motor Cortex; Neurons; Parkinsonian Disorders; Prazosin; Quinpirole; Rats; Rats, Wistar; Receptors, Adrenergic, alpha-1; Receptors, Dopamine D1; Receptors, Dopamine D2

A growing body of evidence indicates that impairment of the ubiquitin-proteasome (UPS) system in the substantia nigra (SN) plays an important role in the pathogenesis of Parkinson's disease (PD). The aim of our study was to compare two unilateral rat models, one produced by intranigral administration of the UPS inhibitor lactacystin or the other induced by 6-OHDA, in terms of their effect on the amphetamine- and apomorphine-induced rotational behavior, striatal dopamine (DA) D1 and D2 receptor sensitivity and tissue levels of DA and its metabolites. We found that these models did not differ in the intensity of ipsilateral rotations induced by amphetamine. In contrast, apomorphine produced contralateral rotations only in 6-OHDA-lesioned rats, and, depending on the dose, it induced either no or moderate ipsilateral rotations in the lactacystin-lesioned group. In addition, lactacystin induced a strong reduction in the tissue DA level and its metabolites in the lesioned striatum and SN when measured three weeks after the administration which was aggravated six weeks post-lesion, reaching the level comparable to the 6-OHDA group. Binding of [3H]raclopride to D2 receptors was increased in the lesioned striatum in both investigated (PD) models six weeks after lesion. In turn, binding of [3H]SCH23390 to the striatal D1 receptors was not changed in the lactacystin group but was increased bilaterally in the 6-OHDA group. The present results add a new value to the study of DA receptor sensitivity and are discussed in the context of the validity of the lactacystin model as a suitable model of Parkinson's disease.

Topics: Acetylcysteine; Amphetamine; Animals; Apomorphine; Benzazepines; Central Nervous System Stimulants; Corpus Striatum; Dopamine; Dopamine Agents; Dose-Response Relationship, Drug; Functional Laterality; Male; Motor Activity; Oxidopamine; Parkinsonian Disorders; Pars Compacta; Raclopride; Rats, Wistar; Receptors, Dopamine D1; Receptors, Dopamine D2; Rotation

Since the discovery of the role of the ubiquitin-proteasome system (UPS) in the pathogenesis of Parkinson's disease, UPS inhibitors, such as lactacystin have been used to investigate the relationship between UPS impairment and degeneration of dopamine (DA) neurons. However, mostly long-term neurotoxic effects of lactacystin have been studied in animal models. Therefore, the aim of our study was to investigate behavioral and biochemical changes related to the DA system during the first week following unilateral intranigral injection of lactacystin to rats. We found that lactacystin produced early spontaneous contralateral rotations which were inhibited by combined administration of DA D1 and D2 receptor antagonists. Simultaneously, an increase in the extracellular level of DA and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) was found in the ipsilateral striatum. In contrast, one week after lesion, when turning behavior was no longer visible, a decrease in the extracellular level of DA, DOPAC and HVA was demonstrated. It was accompanied by a substantial reduction in the tissue levels of DA and its metabolites in the lesioned substantia nigra and striatum. We concluded that unilateral intranigral administration of lactacystin produces an early increase in DA neurotransmission which precedes a decrease in the striatal and nigral tissue DA content. It is manifested by the appearance of spontaneous contralateral rotations and an elevation of the extracellular DA level in the ipsilateral striatum. Since similar behavior was previously observed after intranigral administration of rotenone and MPP(+) but not 6-hydroxydopamine (6-OHDA), it may indicate a common mechanism of action shared by these neurotoxins.

Topics: 3,4-Dihydroxyphenylacetic Acid; Acetylcysteine; Amphetamine; Animals; Benzazepines; Central Nervous System Agents; Corpus Striatum; Dopamine; Dopamine Antagonists; Functional Laterality; Glutamic Acid; Haloperidol; Homovanillic Acid; Male; Movement; Parkinsonian Disorders; Rats, Wistar; Receptors, Dopamine; Rotation; Substantia Nigra

Oscillatory activity in both beta and gamma ranges has been recorded in the subthalamic nucleus (STN) of Parkinson's disease (PD) patients and linked to motor function, with beta activity considered antikinetic, and gamma activity, prokinetic. However, the extent to which nonmotor networks contribute to this activity is unclear. This study uses hemiparkinsonian rats performing a treadmill walking task to compare synchronized STN local field potential (LFP) activity with activity in motor cortex (MCx) and medial prefrontal cortex (mPFC), areas involved in motor and cognitive processes, respectively. Data show increases in STN and MCx 29-36 Hz LFP spectral power and coherence after dopamine depletion, which are reduced by apomorphine and levodopa treatments. In contrast, recordings from mPFC 3 weeks after dopamine depletion failed to show peaks in 29-36 Hz LFP power. However, mPFC and STN both showed peaks in the 45-55 Hz frequency range in LFP power and coherence during walking before and 21 days after dopamine depletion. Interestingly, power in this low gamma range was transiently reduced in both mPFC and STN after dopamine depletion but recovered by day 21. In contrast to the 45-55 Hz activity, the amplitude of the exaggerated 29-36 Hz rhythm in the STN was modulated by paw movement. Furthermore, as in PD patients, after dopamine treatment a third band (high gamma) emerged in the lesioned hemisphere. The results suggest that STN integrates activity from both motor and cognitive networks in a manner that varies with frequency, behavioral state, and the integrity of the dopamine system.

Topics: Action Potentials; Adrenergic Agents; Animals; Antiparkinson Agents; Benzazepines; Cognition Disorders; Disease Models, Animal; Dopamine Antagonists; Evoked Potentials; Functional Laterality; Levodopa; Male; Motor Activity; Oxidopamine; Parkinsonian Disorders; Rats; Rats, Long-Evans; Subthalamic Nucleus; Time Factors; Tyrosine 3-Monooxygenase; Wakefulness

Graft-induced dyskinesia (GID) is a serious complication induced by dopamine (DA) cell transplantation in parkinsonian patients. We have recently shown that DA D2 receptor blockade produces striking blockade of dyskinesia induced by amphetamine in grafted 6-OHDA-lesioned rats, a model of GID. This study was designed to investigate whether blockade of DA D1 receptors could produce similar outcome, and to see whether the effect of these treatments in grafted rats was specific for dyskinesia induced by amphetamine, or could also influence L-DOPA-induced dyskinesia (LID). L-DOPA-primed rats received transplants of fetal DA neurons into the DA-denervated striatum. Beginning at 20weeks after transplantation rats were subjected to pharmacological treatments with either L-DOPA (6mg/kg) or amphetamine (1.5mg/kg) alone, or in combination with the D1 receptor antagonist SCH23390, the D2 receptor antagonist eticlopride, and the 5-HT1A agonist/D2 receptor antagonist buspirone. Grafted rats developed severe GID, while LID was reduced. Both eticlopride and SCH23390 produced near-complete suppression of GID already at very low doses (0.015 and 0.1mg/kg, respectively). Buspirone induced similar suppression at a dose as low as 0.3mg/kg, which is far lower than the dose known to affect LID in non-grafted dyskinetic rats. In agreement with our previous results, the effect of buspirone was independent from 5-HT1A receptor activation, as it was not counteracted by the selective 5-HT1A antagonist WAY100635, but likely due to D2 receptor blockade. Most interestingly, the same doses of eticlopride, SCH23390 and buspirone were found to suppress LID in grafted but not in control dyskinetic rats. Taken together, these data demonstrate that the DA cell grafts strikingly exacerbate the effect of DA D1 and D2 receptor blockade against both GID and LID, and suggest that the anti-GID effect of buspirone seen in patients may also be due to blockade of DA D2 receptors.

Topics: Amphetamine; Animals; Anti-Dyskinesia Agents; Antiparkinson Agents; Benzazepines; Buspirone; Disease Models, Animal; Dopamine Agonists; Dopamine Antagonists; Dopamine D2 Receptor Antagonists; Dopaminergic Neurons; Dyskinesia, Drug-Induced; Female; Indoles; Levodopa; Mesencephalon; Parkinsonian Disorders; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1; Receptors, Dopamine D2; Salicylamides; Serotonin Receptor Agonists

Parkinson's disease (PD) patients exhibit motor and non-motor symptoms that severely affect quality of life. Cognitive alterations in PD subjects have been related to both structural and functional hippocampal changes. Here we investigated the effects of the 6-hydroxydopamine (6-OHDA) lesion in the Medial Forebrain Bundle (MFB) on the hippocampus focusing on the Dentate Gyrus (DG). In vivo microdialysis measurements revealed that the 6-OHDA injection disrupts both dopaminergic and noradrenergic transmission in rat DG. In vitro electrophysiological recordings showed that these neurochemical alterations were accompanied by impairment of long-term depression (LTD) at medial perforant path/DG synapses. Furthermore, this alteration was reversed by l-DOPA treatment. Notably, the therapeutic effect of l-DOPA on LTD was blocked by the antagonism of β-noradrenergic receptors, but not by dopamine D1 or D2 receptor antagonists. Thus, while the dopaminergic transmission does not seem to be implicated in this therapeutic effect of l-DOPA, the noradrenergic system plays a central role in the synaptic dysfunction of the DG in experimental PD. Our work provides new evidence on the role of catecholamines in DG synaptic plasticity and sheds light on the possible synaptic mechanisms underlying cognitive deficits in PD. Furthermore, our results indicate that l-DOPA exerts a therapeutic effect on the parkinsonian brain through different, coexistent, mechanisms.

Topics: Animals; Antiparkinson Agents; Benzazepines; Dentate Gyrus; Disease Models, Animal; Dopamine; Dopamine Antagonists; Electric Stimulation; Functional Laterality; Levodopa; Long-Term Synaptic Depression; Male; Microdialysis; Norepinephrine; Oxidopamine; Parkinsonian Disorders; Rats; Rats, Wistar; Sulpiride

Dopamine depletion in Parkinson's disease (PD) results in bradykinesia and tremor. Therapeutic administration of the dopamine precursor, l-Dopa, alleviates these symptoms but dyskinesia's can manifest with chronic treatment. In the MPTP toxin mouse model of PD, lesion severity is often assessed by the rotarod behavioral assay. Dopamine depletion by MPTP is thought to induce rotarod behavioral decline. Here we surveyed rotarod behavior and striatal dopamine at timed intervals post-MPTP. Paradoxically, rotarod disability coincided with gradual striatal dopamine restoration. l-Dopa supplementation exacerbated rotarod disability, whereas dopamine antagonism restored performance.. dopamine restoration, not depletion, precipitates rotarod disability after MPTP intoxication, and caution should be applied when using this assay for MPTP.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; Animals; Benzazepines; Dopamine; Dopamine Agents; Levodopa; Male; Mice; Mice, Inbred C57BL; Motor Activity; Parkinsonian Disorders; Receptors, Dopamine D1; Rotarod Performance Test; Time Factors

L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia (LID) remains a challenge in Parkinson's disease (PD) drug therapy. In the present study, we examined the effect of L-stepholidine (L-SPD), a known dual dopamine receptor agent, on LID in 6-hydroxydopamine (6-OHDA)-lesioned PD rat model. Daily administration of L-DOPA to PD rats for 22 days induced steady expression of LID, co-administration of L-SPD with L-DOPA significantly ameliorated LID without compromising the therapeutic potency of L-DOPA, indicating that L-SPD attenuated LID development. L-SPD alone elicited stable contralateral rotational behavior without inducing significant dyskinesia. Acute administration of L-SPD to rats with established LID produced significant relief of dyskinesia; this effect was mimicked by D(2) receptor antagonist haloperidol, but blunted by 5-HT(1A) receptor antagonist WAY100635. Furthermore, the mRNA level of 5-HT(1A) decreased significantly on 6-OHDA-lesioned striata, whereas chronic L-SPD treatment restored 5-HT(1A) receptor mRNA level on the lesioned striata. The present data demonstrated that L-SPD elicited antidyskinesia effects via both dopamine (D(2) receptor antagonistic activity) and nondopamine (5-HT(1A) agonistic activity) mechanisms.

Topics: 8-Hydroxy-2-(di-n-propylamino)tetralin; Analysis of Variance; Animals; Antiparkinson Agents; Antipsychotic Agents; Benzazepines; Berberine; CHO Cells; Corpus Striatum; Cricetinae; Cricetulus; Disease Models, Animal; Dopamine Agents; Drug Administration Schedule; Drug Interactions; Dyskinesias; Gene Expression Regulation; Levodopa; Male; Oxidopamine; Parkinsonian Disorders; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT1A; RNA, Messenger; Serotonin Receptor Agonists; Transfection; Tritium

Parkinson's disease (PD) is due to widespread degeneration in the central and peripheral nervous systems. The hallmark pathology remains in the dopaminergic striatal insufficiency and degeneration of dopaminergic neurons in the substantia nigra.. The present study analysed the effect of serotonin (5-HT), dopamine, and norepinephrine as treatment on rotenone induced hemi-Parkinson's disease in rats and its role in the regulation of dopamine receptor subtypes in the corpus striatum of the experimental rats.. Unilateral stereotaxic single-dose infusions of rotenone were administered to the substantia nigra of adult male Wistar rats. Neurotransmitters serotonin (5-HT), dopamine, and norepinephrine treatments were given to rotenone induced hemi-Parkinson's rats. Dopamine receptor and its subtypes (D₁ and D₂) binding assay were carried out. Gene expression studies of dopamine D₁ and D₂ were carried out using real-time PCR.. Scatchard analysis of dopamine and dopamine D₂ receptor showed a significant increase (P<0.001) and dopamine D₁ receptor showed a significant decrease (P<0.001) in the B(max) in corpus striatum of the PD rats compared to control. These altered parameters were reversed to near control in the serotonin- and norepinephrine-treated PD rats and no change was observed in dopamine-treated PD rats. Real-time PCR results confirmed the receptor data.. Our results showed that serotonin and norepinephrine functionally reversed in dopamine receptors in rotenone-induced hemi-Parkinson's rat. This has clinical significance in the therapeutic management of PD.

Topics: Animals; Benzamides; Benzazepines; Catecholamines; Corpus Striatum; Disease Models, Animal; Dopamine; Dopamine Antagonists; Dopamine D2 Receptor Antagonists; Drug Interactions; Functional Laterality; Male; Norepinephrine; Parkinsonian Disorders; Protein Binding; Radionuclide Imaging; Rats; Rats, Wistar; Receptors, Dopamine D1; Receptors, Dopamine D2; Rotarod Performance Test; Rotenone; Serotonin; Tritium

Angiogenesis occurs in the brains of Parkinson's disease patients, but the effects of dopamine replacement therapy on this process have not been examined. Using rats with 6-hydroxydopamine lesions, we have compared angiogenic responses induced in the basal ganglia by chronic treatment with either L-DOPA, or bromocriptine, or a selective D1 receptor agonist (SKF38393). Moreover, we have asked whether L-DOPA-induced angiogenesis can be blocked by co-treatment with either a D1- or a D2 receptor antagonist (SCH23390 and eticlopride, respectively), or by an inhibitor of extracellular signal-regulated kinases 1 and 2 (ERK1/2) (SL327). L-DOPA, but not bromocriptine, induced dyskinesia, which was associated with endothelial proliferation, upregulation of immature endothelial markers (nestin) and downregulation of endothelial barrier antigen in the striatum and its output structures. At a dose inducing dyskinesia (1.5 mg/kg/day), SKF38393 elicited angiogenic changes similar to L-DOPA. Antagonism of D1- but not D2 class receptors completely suppressed both the development of dyskinesia and the upregulation of angiogenesis markers. In fact, L-DOPA-induced endothelial proliferation was markedly exacerbated by low-dose D2 antagonism (0.01 mg/kg eticlopride). Inhibition of ERK1/2 by SL327 attenuated L-DOPA-induced dyskinesia and completely inhibited all markers of angiogenesis. These results highlight the specific link between treatment-induced dyskinesias and microvascular remodeling in the dopamine-denervated brain. L-DOPA-induced angiogenesis requires stimulation of D1 receptors and activation of ERK1/2, whereas the stimulation of D2 receptors seems to oppose this response.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Aminoacetonitrile; Animals; Antiparkinson Agents; Basal Ganglia; Benzazepines; Bromocriptine; Disease Models, Animal; Dopamine Agents; Dopamine D2 Receptor Antagonists; Extracellular Signal-Regulated MAP Kinases; Female; Levodopa; Neovascularization, Pathologic; Oxidopamine; Parkinsonian Disorders; Protease Inhibitors; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1; Receptors, Dopamine D2; Salicylamides