Neuroleptic-induced catalepsy as a model of Parkinson's disease. I. Effect of dopaminergic agents

The curative and mechanistic acumen of curcuminoids formulations against haloperidol induced Parkinson's disease animal model

Parkinson's disease (PD) is slowly developing neurodegenerative disorder associated with gradual decline in cerebration and laboriousness to perform routine piece of work. PD imposed a social burden on society through higher medical cost and by loss of social productivity in current era. The available treatment options are expensive and associated with serious adverse effect after long term use. Therefore, there is a critical clinical need to develop alternative pharmacotherapies from natural sources to prevent and cure the pathological hall marks of PD with minimal cost. Our study aimed to scrutinize the antiparkinsonian potential of curcuminoids-rich extract and its binary and ternary inclusion complexes. In healthy rats, 1 mg/kg haloperidol daily intraperitoneally, for 3 weeks was used to provoke Parkinsonism like symptoms except control group. Curcuminoids rich extract, binary and ternary inclusion complexes formulations 15-30 mg/kg, L-dopa and carbidopa (100 + 25 mg/kg) were orally administered on each day for 3 weeks. Biochemical, histopathological and RT-qPCR analyses were conducted after neurobehavioral observations. Findings of current study indicated that all curcuminoids formulations markedly mitigated the behavioral abnormalities, recovered the level of antioxidant enzymes, acetylcholinesterase inhibitory activity and neurotransmitters. Histological analysis revealed that curcuminoids supplements stabilized the neuronal loss, pigmentation and Lewy bodies' formation. The mRNA expressions of neuro-inflammatory and specific PD pathological biomarkers were downregulated by treatment with curcuminoids formulations. Therefore, it is suggested that these curcuminoids rich extract, binary and ternary supplements should be considered as promising therapeutic agents in development of modern anti-Parkinson's disease medications.

Systems pharmacology based approach to investigate the in-vivo therapeutic efficacy of Albizia lebbeck (L.) in experimental model of Parkinson's disease

Background

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by loss of dopaminergic neurons in substantia nigra pars compacta and clinically manifested mainly with motor dysfunctions. Plants are rich source of medicinally important bioactive compounds and inhabitants of underdeveloped countries used plants for treatment of various ailments. Albizia lebbeck has been reported to possess antioxidant and neuroprotective properties that suggest the evaluation of its traditional therapeutic potential in neurodegenerative diseases.

The aim of present study was to validate the traditional use of Albizia lebbeck (L.) and delineate its mechanism of action in PD. The systems pharmacology approach was employed to explain the Albizia lebbeck (L.) mechanism of action in PD.

Methods

The haloperidol-induced catalepsy was adopted as experimental model of PD for in-vivo studies in wistar albino rats. The systems pharmacology approach was employed to explain the Albizia lebbeck (L.) mechanism of action in PD.

Results

In-vivo studies revealed that Albizia lebbeck improved the motor functions and endurance as demonstrated in behavioral studies which were further supported by the rescue of endogenous antioxidant defense and reversal of ultrastructural damages in histological studies. System pharmacology approach identified 25 drug like compounds interacting with 132 targets in a bipartite graph that revealed the synergistic mechanism of action at system level. Kaemferol, phytosterol and okanin were found to be the important compounds nodes with prominent target nodes of TDP1 and MAPT.

Conclusion

The therapeutic efficiency of Albizia lebbeck in PD was effectively delineated in our experimental and systems pharmacology approach. Moreover, this approach further facilitates the drug discovery from Albizia lebbeck for PD.

Haloperidol-induced parkinsonism is attenuated by varenicline in mice

Background Parkinson's disease (PD) is a neurodegenerative disorder of the central nervous system (CNS). However, there is no known drug to stop/slow down this neurodegeneration. Varenicline is an anti-smoking drug and has the potential to prevent neurodegeneration. Thus, the present study was designed to evaluate the effect of varenicline in animal models of PD. Methods Levodopa and haloperidol were administered in doses of 30 and 1 mg/kg, intraperitoneally (i.p.), respectively. Group 1 was administered haloperidol; groups 2, 3 and 4 were administered haloperidol along with varenicline in doses of 0.5, 1.5 and 2.5 mg/kg, i.p., respectively and group 5 was administered levodopa along with haloperidol. Varenicline was administered daily, 30 min prior to the administration of haloperidol. Varenicline was administered for the first 8 days, and then from the 9th day until the 15th day. Behavioral assessment (rotarod and catalepsy tests) was performed on days 9 and 15. Assessment of striatal dopamine levels and histopathology were also performed. Results In the haloperidol-treated groups, significant decrease in latency to fall off (on rotarod) and increase in catalepsy duration (in catalepsy test) were observed as compared to the control group. In the levodopa-treated group, significant increase in latency to fall off the rotarod and significant decrease in catalepsy duration were observed as compared to the haloperidol-treated groups. Further, on day 9, varenicline (2.5 mg/kg) significantly increased the latency to fall off the rotarod, while varenicline (0.5 and 1.5 mg/kg) did not cause any significant change in latency to fall off the rotarod as compared to the haloperidol-treated group. On day 15, significant increase in latency to fall off the rotarod was observed in varenicline (at all doses) as compared to the haloperidol-treated group. In the catalepsy test, the varenicline-treated (at all doses) groups showed significant decrease in duration of catalepsy on day 9 and day 15 as compared to the haloperidol-treated group. Significant decrease in striatal dopamine levels was observed among the haloperidol-treated groups as compared to the control group. Further, varenicline-treated (at all doses) and levodopa-treated groups showed significant increase in striatal dopamine levels when compared with the haloperidol-treated group. In histology, varenicline (0.5 mg/kg) showed moderate decrease in neurons, while varenicline (1.5 and 2.5 mg/kg) showed mild decrease in neurons. However, the levodopa-treated group did not show any significant decrease in neurons. Thus, varenicline has shown promising results and has provided novel strategy for the treatment of PD.

Neuroprotective potential of Beta vulgaris L. in Parkinson's disease

Objective:

The objective was to investigate the neuroprotective role of Beta vulgaris in Parkinson's disease (PD).

Materials and Methods:

PD was induced by administration of reserpine (5 mg/kg/day, i.p for 5 consecutive days), haloperidol (1 mg/kg, i.p.), and tacrine (2.5 mg/kg, i.p.) in experimental animals. The symptoms of PD such as tremors, akinesia, rigidity, catalepsy, and vacuous chewing movements (VCMs) were evaluated. Foot shock-induced aggression (FSIA) model was used to confirm anti-parkinsonian activity. The methanolic extract of Beta vulgaris (MEBV) was administered at doses of 100, 200, and 300 mg/kg, p.o. The combination of L-dopa and carbidopa was used as a standard drug. Behavioral studies such as locomotor activity and grip strength were determined, and oxidative stress was evaluated in FSIA model in rat brain.

Results:

Pretreatment with MEBV (200 and 300 mg/kg) significantly reduced the intensity of muscular rigidity, duration of catalepsy, akinesia, the number of tremors, VCMs, and increase fighting behavior. The locomotor activity and grip strength were significantly increased by MEBV. In FSIA, the biochemical analysis of brain revealed the increased level of lipid peroxidation (LPO) and decreased levels of superoxide dismutase (SOD) and catalase (CAT). MEBV significantly reduced LPO level and restored the defensive antioxidant enzymes SOD and CAT in rat brain.

Conclusions:

The results indicated the protective role of B. vulgaris against PD. The mechanism of protection may be due to augmentation of cellular antioxidants.

Anti-Parkinson Activity of Petroleum Ether Extract of Ficus religiosa (L.) Leaves

In the present study, we evaluated anti-Parkinson's activity of petroleum ether extract of Ficus religiosa (PEFRE) leaves in haloperidol and 6 hydroxydopamine (6-OHDA) induced experimental animal models. In this study, effects of Ficus religiosa (100, 200, and 400 mg/kg, p.o.) were studied using in vivo behavioral parameters like catalepsy, muscle rigidity, and locomotor activity and its effects on neurochemical parameters (MDA, CAT, SOD, and GSH) in rats. The experiment was designed by giving haloperidol to induce catalepsy and 6-OHDA to induce Parkinson's disease-like symptoms. The increased cataleptic scores (induced by haloperidol) were significantly (p < 0.001) found to be reduced, with the PEFRE at a dose of 200 and 400 mg/kg (p.o.). 6-OHDA significantly induced motor dysfunction (muscle rigidity and hypolocomotion). 6-OHDA administration showed significant increase in lipid peroxidation level and depleted superoxide dismutase, catalase, and reduced glutathione level. Daily administration of PEFRE (400 mg/kg) significantly improved motor performance and also significantly attenuated oxidative damage. Thus, the study proved that Ficus religiosa treatment significantly attenuated the motor defects and also protected the brain from oxidative stress.

Pharmacological characteristics of zolpidem-induced catalepsy in the rat

Zolpidem is a non-benzodiazepine hypnotic drug acting preferentially at α1-containing GABAA receptors expressed in various parts of the brain, including the basal ganglia. The aim of the present study was to provide preliminary characteristics of zolpidem-induced catalepsy in Wistar rats. Zolpidem (2.5-10.0mg/kg), but not diazepam and midazolam, produced dose-dependent cataleptic responses in the bar test, which were similar to those produced by a reference antipsychotic drug, haloperidol. Zolpidem-induced catalepsy was abolished by a benzodiazepine site antagonist, flumazenil (5.0mg/kg), D2/3 receptor agonist, quinpirole (1.0mg/kg), and a non-competitive NMDA receptor antagonist, MK-801 (0.1mg/kg), but not by a non-selective opioid receptor antagonist, naltrexone (3.0mg/kg). The present results indicate that systemic injections of zolpidem may produce short-lasting, neuroleptic-like catalepsy in the rat.

Haloperidol conditioned catalepsy in rats: a possible role for D1-like receptors

Decreases in brain dopamine (DA) lead to catalepsy, quantified by the time a rat remains with its forepaws resting on a suspended horizontal bar. Low doses of the DA D2 receptor-preferring antagonist haloperidol repeatedly injected in a particular environment lead to gradual day-to-day increases in catalepsy (catalepsy sensitization) and subsequent testing following an injection of saline reveal conditioned catalepsy. We tested the hypothesis that D1-like and D2 receptors play different roles in catalepsy sensitization and in acquisition and expression of conditioned catalepsy. Rats were repeatedly treated with the DA D1-like receptor antagonist SCH 23990 (0.05, 0.1 and 0.25 mg/kg i.p.), the D2 receptor-preferring antagonist haloperidol (0.1, 0.25 and 0.5 mg/kg i.p.) or a combination of the two drugs and tested for catalepsy each day in the same environment. Following 10 drug treatment days, rats were injected with saline and tested for conditioned catalepsy in the previously drug-paired environment. Haloperidol did not elicit cataleptic responses in the initial session; however, rats developed sensitization with repeated testing. Significant catalepsy sensitization was not observed in rats repeatedly tested with SCH 23390. When rats were injected and tested with saline following haloperidol sensitization they exhibited conditioned catalepsy in the test environment; conditioned catalepsy was not seen following SCH 23390. Rats treated with 0.05 mg/kg SCH 23390+0.25 mg/kg haloperidol showed catalepsy sensitization but failed to show conditioned catalepsy. Conversely, SCH 23390 (0.05 mg/kg) given on the test day after sensitization to haloperidol (0.25 mg/kg) failed to block conditioned catalepsy. Repeated antagonism of D2 receptors leads to catalepsy sensitization with repeated testing in a specific environment. Conditioned catalepsy requires intact D1-like receptor function during sensitization sessions but not during test sessions. In conclusion, repeated antagonism of D2, but not D1-like receptors leads to catalepsy sensitization with repeated testing in a specific environment. Conditioned catalepsy requires functional D1-like receptors during sensitization sessions but not during test sessions.

Animal models of Parkinson's disease: a source of novel treatments and clues to the cause of the disease

Animal models of Parkinson's disease (PD) have proved highly effective in the discovery of novel treatments for motor symptoms of PD and in the search for clues to the underlying cause of the illness. Models based on specific pathogenic mechanisms may subsequently lead to the development of neuroprotective agents for PD that stop or slow disease progression. The array of available rodent models is large and ranges from acute pharmacological models, such as the reserpine- or haloperidol-treated rats that display one or more parkinsonian signs, to models exhibiting destruction of the dopaminergic nigro-striatal pathway, such as the classical 6-hydroxydopamine (6-OHDA) rat and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models. All of these have provided test beds in which new molecules for treating the motor symptoms of PD can be assessed. In addition, the emergence of abnormal involuntary movements (AIMs) with repeated treatment of 6-OHDA-lesioned rats with L-DOPA has allowed for examination of the mechanisms responsible for treatment-related dyskinesia in PD, and the detection of molecules able to prevent or reverse their appearance. Other toxin-based models of nigro-striatal tract degeneration include the systemic administration of the pesticides rotenone and paraquat, but whilst providing clues to disease pathogenesis, these are not so commonly used for drug development. The MPTP-treated primate model of PD, which closely mimics the clinical features of PD and in which all currently used anti-parkinsonian medications have been shown to be effective, is undoubtedly the most clinically-relevant of all available models. The MPTP-treated primate develops clear dyskinesia when repeatedly exposed to L-DOPA, and these parkinsonian animals have shown responses to novel dopaminergic agents that are highly predictive of their effect in man. Whether non-dopaminergic drugs show the same degree of predictability of response is a matter of debate. As our understanding of the pathogenesis of PD has improved, so new rodent models produced by agents mimicking these mechanisms, including proteasome inhibitors such as PSI, lactacystin and epoximycin or inflammogens like lipopolysaccharide (LPS) have been developed. A further generation of models aimed at mimicking the genetic causes of PD has also sprung up. Whilst these newer models have provided further clues to the disease pathology, they have so far been less commonly used for drug development. There is little doubt that the availability of experimental animal models of PD has dramatically altered dopaminergic drug treatment of the illness and the prevention and reversal of drug-related side effects that emerge with disease progression and chronic medication. However, so far, we have made little progress in moving into other pharmacological areas for the treatment of PD, and we have not developed models that reflect the progressive nature of the illness and its complexity in terms of the extent of pathology and biochemical change. Only when this occurs are we likely to make progress in developing agents to stop or slow the disease progression. The overarching question that draws all of these models together in the quest for better drug treatments for PD is how well do they recapitulate the human condition and how predictive are they of successful translation of drugs into the clinic? This article aims to clarify the current position and highlight the strengths and weaknesses of available models.

Role of nitric oxide on motor behavior

The present review paper describes results indicating the influence of nitric oxide (NO) on motor control. Our last studies showed that systemic injections of low doses of inhibitors of NO synthase (NOS), the enzyme responsible for NO formation, induce anxiolytic effects in the elevated plus maze whereas higher doses decrease maze exploration. Also, NOS inhibitors decrease locomotion and rearing in an open field arena. These results may involve motor effects of this compounds, since inhibitors of NOS, NG-nitro-L-arginine (L-NOARG), N(G)-nitro-L-arginine methylester (L-NAME), N(G)-monomethyl-L-arginine (L-NMMA), and 7-Nitroindazole (7-NIO), induced catalepsy in mice. This effect was also found in rats after systemic, intracebroventricular or intrastriatal administration. Acute administration of L-NOARG has an additive cataleptic effect with haloperidol, a dopamine D2 antagonist. The catalepsy is also potentiated by WAY 100135 (5-HT1a receptor antagonist), ketanserin (5HT2a and alfal adrenergic receptor antagonist), and ritanserin (5-HT2a and 5HT2c receptor antagonist). Atropine sulfate and biperiden, antimuscarinic drugs, block L-NOARG-induced catalepsy in mice. L-NOARG subchronic administration in mice induces rapid tolerance (3 days) to its cataleptic effects. It also produces cross-tolerance to haloperidol-induced catalepsy. After subchronic L-NOARG treatment there is an increase in the density NADPH-d positive neurons in the dorsal part of nucleus caudate-putamen, nucleus accumbens, and tegmental pedunculupontinus nucleus. In contrast, this treatment decreases NADPH-d neuronal number in the substantia nigra compacta. Considering these results we suggest that (i) NO may modulate motor behavior, probably by interfering with dopaminergic, serotonergic, and cholinergic neurotransmission in the striatum; (ii) Subchronic NO synthesis inhibition induces plastic changes in NO-producing neurons in brain areas related to motor control and causes cross-tolerance to the cataleptic effect of haloperidol, raising the possibility that such treatments could decrease motor side effects associated with antipsychotic medications. Finally, recent studies using experimental Parkinson's disease models suggest an interaction between NO system and neurodegenerative processes in the nigrostriatal pathway. It provides evidence of a protective role of NO. Together, our results indicate that NO may be a key participant on physiological and pathophysiological processes in the nigrostriatal system.

Serotonin modulation of catalepsy induced by N(G)-nitro-L-arginine in mice

N(G)-(Nitro-L-arginine (L-NOARG), an inhibitor of nitric oxide synthase, induces catalepsy in mice. The objective of the present work was to investigate if serotonergic drugs are able to modulate this effect. Results showed that the cataleptogenic effect of L-NOARG (40 mg/kg) in male albino-Swiss mice was enhanced by pre-treatment with (+)-N-tert-butyl-3-(4-[2-methoxyphenyl]piperazin-1-yl)-2-phenylpro panamide ((+)-WAY-100135, 5 or 10 mg/kg), a 5-HT1A-selective receptor antagonist, and by ketanserin (5 or 10 mg/kg), a 5-HT2A receptor and alpha1-adrenoceptor antagonist. Prazosin (3 or 5 mg/kg), an alpha1-adrenoceptor antagonist, and endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3yl)-2,3-dihydro-3,3-dimet hyl-indole-1-carboxamide HCl (BRL-46470A, 0.05 or 0.5 mg/kg), a 5-HT3 receptor antagonist, did not interfere with L-NOARG-induced catalepsy. Ritanserin (3 or 10 mg/kg), a 5-HT2A and 5-HT2C receptor antagonist, tended to enhance the effect of L-NOARG. These results confirm that interference with the formation of nitric oxide induces catalepsy in mice, and suggest that this effect is modulated by 5-HT1A and 5-HT2A receptors.

Serotonergic mechanisms in neuroleptic-induced catalepsy in the rat

The present paper reviews a series of experiments aimed at elucidating the interaction between specific dopamine (DA) and 5-hydroxytryptamine (5-HT) receptors in the mediation of extrapyramidal motor functions in the rat. There is strong evidence to suggest that (1) the catalepsy produced by dopamine D1 or D2 receptor antagonists can be completely antagonized by the administration of 5-HT1A receptor agonists acting at 5-HT autoreceptors in the median raphe nucleus; (2) the catalepsy produced by a dopamine D2 receptor antagonist can be completely antagonized by treatment with a 5-HT2A/C receptor agonist; and (3) the catalepsy produced by blockade of either dopamine D1 or D2 receptors is not affected by the administration of a 5-HT2A/C receptor antagonist. The emerging picture of DA/5-HT receptor interactions in the mediation of extrapyramidal motor functions is of great interest in relation to present efforts to develop new atypical neuroleptics with affinity for brain 5-HT receptor subtypes, and also for the observations that new serotonin selective re-uptake inhibiting antidepressants can produce parkinson-like symptoms in vulnerable individuals.

Role of striatal dopamine D2 receptors in the paw test, an animal model for the therapeutic efficacy and extrapyramidal side effects of neuroleptic drugs

The effect of administration of the D2 antagonist sulpiride in three striatal areas (dorsal striatum, DS; nucleus accumbens, ACC; olfactory tubercle; OT) was studied in the so-called paw test. In the paw test two parameters are measured (the hindlimb retraction time (HRT) and the forelimb retraction time (FRT)) that model the therapeutic efficacy and the extrapyramidal side effects of neuroleptics, respectively. Sulpiride significantly enhanced the HRT in each of the three structures. Identical doses of sulpiride administered in the three structures produced similar effects. The FRT was enhanced after administration of sulpiride in the DS and in the ACC. The minimal effective dose was lower for the DS. Administration of sulpiride in the OT did not affect the FRT. The effects on the FRT were very slow in onset (strong effects 4 h or more following administration of sulpiride), especially in comparison to the rapid effect on FRT following systemic administration of classical neuroleptics. To analyze this slowness of effect, two additional experiments were performed: first, the inter-trial time was changed so that it was identical to that used in systemic studies; second, sulpiride was administered simultaneously in the DS and the ACC. Neither experiment produced an earlier effect on the FRT. The present data provide additional evidence for the theory that regional selectivity of drugs determines their propensity to induce extrapyramidal side effects. However, the data also suggest that the generally held view that the dorsal striatum is solely responsible for the extrapyramidal side effects of neuroleptic drugs is too simple.

Felbamate, an anti-convulsive drug, has anti-parkinsonian potential in rats

The potency of felbamate, an anti-convulsive drug, to influence dopamine D1 (SCH 23390) and D2 (haloperidol) receptor-mediated catalepsy (akinesia and bradykinesia) was studied in rats. In the catalepsy test, felbamate antagonized dopamine D2 receptor- but not D1 receptor-induced akinesia. Bradykinesia in the open field was never influenced. The results demonstrate that felbamate has similar anti-parkinsonian potential as glycine site antagonists blocking the N-methyl-D-aspartate (NMDA) receptor complex.

Discrete quinolinic acid lesions of the lateral but not of the medial caudate-putamen reversed haloperidol-induced catalepsy in rats

Discrete lesions in the medial or lateral subregion of the rostral caudate-putamen (CP) were induced by bilateral intracerebral injections of a low dose of quinolinic acid (30 nmol in 1 microliter/per side) in rats. Quinolinic acid lesions in the lateral CP potently reversed haloperidol-induced catalepsy (0.5 mg/kg,i.p.), while lesions in the medial CP were not effective. Spontaneous locomotor activity was not altered significantly after quinolinic acid lesions of either the medial or lateral CP. These results show that the lateral CP seems to be important for the expression of neuroleptic-induced catalepsy and thus further corroborate the concept of a functional heterogeneity of the striatum.