Anticataleptic Effect Research Articles

Fluoxetine improves the effect of levodopa on 6-hydroxy dopamine-induced motor impairments in rats.

Long term L-DOPA therapy in Parkinson's disease is associated with troublesome motor fluctuations such as L -DOPA Induced dyskinesia and wearing off effect. Our recent study showed that activation of 5-HT1A receptors could improve the anti-cataleptic effect of L-DOPA in parkinsonian rats. In this study we investigated the effect of fluoxetine on anti-parkinsonian effect of L-DOPA in 6-hydroxydopamine (6-OHDA)-lesioned rats. Catalepsy and motor incoordination were induced by unilateral injection of 6-OHDA (8μg/2μl/rat) into the central region of the sabstantia nigra pars compacta (SNc). After 3 weeks as a recovery period, these rats injected intraperitoneally (i.p.) L-DOPA (15 mg/kg) twice daily for 20 consecutive days, and anti-parkinsonian effect of L-DOPA was investigated by bar-test and rotarod on days 5, 10, 15 and 20. The results showed that L-DOPA is able to improve motor coordination in rotarod only until day 15 and these effects of L-DOPA were abolished on the day 20. On day 21, rats were co-injected with fluoxetine (0.1, 0.5 and 1mg/kg, i.p.) and L-DOPA (15 mg/kg, i.p.). Fluoxetine increased anti-cataleptic effect of L-DOPA at the dose of 1 mg/kg, while fluoxetine had not any impact on the effect of L-DOPA in rotarod test. The effect of fluoxetine (1 mg/kg, i.p.) on anti-cataleptic effect of L-DOPA (15 mg/kg, i.p.) was reversed by 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl) piperazine hydrobromide (NAN-190; 0.5 mg/kg, i.p.), as a 5-HT1A receptor antagonist. According to the results, it may be concluded that fluoxetine improves 6-OHDA-induced catalepsy and motor imbalance in L-DOPA- treated rats through activation of 5-HT1A. Further studies should be designed to clarify the precise mechanism of interaction between 5-HT1A and dopaminergic neurons.

The effect of chronic administration of buspirone on 6-hydroxydopamine-induced catalepsy in rats.

Several evidences show that serotonergic neurons play a role in the regulation of movements executed by the basal ganglia. Recently we have reported that single dose of buspirone improved 6-hydroxydopamine (6-OHDA) and haloperidol-induced catalepsy. This study is aimed to investigate effect of chronic intraperitoneal (i.p.) administration of buspirone on 6-OHDA-induced catalepsy in male Wistar rats. Catalepsy was induced by unilateral infusion of 6-OHDA (8 μg/2 μl/rat) into the central region of the SNc and was assayed by the bar-test method 5, 60, 120 and 180 min after drugs administration in 10th day. The effect of buspirone (0.5, 1 and 2 mg/kg, i.p. for 10 days) was assessed in 6-OHDA-lesioned rats. The results showed that chronic injection of buspirone (0.5, 1 and 2 mg/kg, i.p. for 10 days) decreased catalepsy when compared with the control group. The best anticataleptic effect was observed at the dose of 1 mg/kg. The catalepsy-improving effect of buspirone was reversed by 1-(2-methoxyphenyl)- 4-[4-(2-phthalimido) butyl]piperazine hydrobromide (NAN-190), 0.5 mg/kg, i.p.,as a 5-HT1A receptor antagonist. Our study indicates that chronic administration of buspirone improves catalepsy in a 6-OHDA-induced animal model of parkinson's disease (PD). We also suggest that buspirone may be used as an adjuvant therapy to increase effectiveness of antiparkinsonian drugs. In order to prove this hypothesis, further clinical studies should be done.

Role of 5-Hydroxytryptamine 1A Receptors in 6-Hydroxydopmaine-induced Catalepsy-like Immobilization in Rats: a Therapeutic Approach for Treating Catalepsy of Parkinson's Disease.

We have shown that buspirone, a partial agonist of 5-hydroxytryptamine 1A (5-HT1A) receptors, improves motor dysfunctions induced by 6-hydroxydopamine (6-OHDA) and haloperidol in rats. The present work extends these findings by investigating the role of 5-HT1A receptors on catalepsy-like immobilization in rats, a model of Parkinson's disease. Catalepsy was induced by unilateral infusion of 6-OH-dopamine (8 μg/2μL/rat) into the central region of the substantia nigra, compact part (SNc) and assayed by bar-test method 5, 60, 120 and 180 min after the drugs administration. The involvement of 5-HT1A receptors in 6-OHDA-induced catalepsy was studied through intraperitoneal (0.25, 0.5 and 1mg/Kg IP) and intrasubstantia nigra, compact part (10 μg/rat, intra-SNc) injection of 8-hydroxy-2-[di-n-propylamino] tetralin (8-OHDPAT) as well as administration of 1-(2-methoxyphenyl)-4-[4-(2-pthalimmido) butyl] piperazine hydrobromide (0.1, 0.5 and 1 mg/Kg, NAN-190, IP). NAN-190 (1 mg/Kg, IP) and 8-OHDPAT (1 mg/Kg, IP and 10 μg/rat, intra-SNc) increased and decreased 6-OHDA-induced catalepsy respectively. In normal (non 6-OHDA-lesioned) rats, NAN-190 (1 mg/Kg, IP) increased the elapsed time in bar-test while 8-OHDPAT did not produce any significant effect. The anticataleptic effect of 8-OHDPAT (1 mg/Kg, IP) was reversed markedly by co-injection with NAN-190 (1 mg/Kg, IP). These findings suggest that 5-HT1A receptors are involved in 6-OHDA-induced catalepsy-like immobilization.

Antidepressant-Like Effects of Central BDNF Administration in Mice of Antidepressant Sensitive Catalepsy (ASC) Strain

Although numerous data evidence the implication of brain-derived neurotrophic factor (BDNF) in the pathophysiology of depression, the potential for BDNF to correct genetically defined depressive-like states is poorly studied. This study was aimed to reveal antidepressant-like effects of BDNF (300 ng, 2×, i.c.v.) on behavior and mRNA expression of genes associated with depression-like state in the brain in mice of antidepressant sensitive catalepsy (ASC) strain characterized by high hereditary predisposition to catalepsy and depressive-like features. Behavioral tests were held on the 7th-16th days after the first (4th-13th after the second) BDNF injection. Results showed that BDNF normalized impaired sexual motivation in the ASC males, and this BDNF effect differed, with advantageous effects, from that of widely used antidepressants. The anticataleptic effect of two BDNF injections was enhanced compared with a single administration. A tendency to decrease the immobility duration in tail-suspension test was observed in BDNF-treated ASC mice. The effects on catalepsy and sexual motivation were specific since BDNF did not alter locomotor and exploratory activity or social interest in the ASC mice. Along with behavioral antidepressant-like effects on the ASC mice, BDNF increased hippocampal mRNA levels of Bdnf and Creb1 (cAMP response element-binding protein gene). BDNF also augmented mRNA levels of Arc gene encoding Arc (Activity-regulated cytoskeleton-associated) protein involved in BDNF-induced processes of neuronal and synaptic plasticity in hippocampus and prefrontal cortex. The data suggest that: [1] BDNF is effective in the treatment of some genetically defined behavioral disturbances; [2] BDNF influences sexually-motivated behavior; [3] Arc mRNA levels may serve as a molecular marker of BDNF physiological activity associated with its long-lasting behavioral effects; [4] ASC mouse strain can be used as a suitable model to study mechanisms of BDNF effects on hereditary-dependent behavioral disorders.

P.1.c.036 Lipopolysaccharide -induced oxidative stress in rat striatum

Studies have shown that 5-HT1A receptor ligands modulate antipsychotic-induced catalepsy. Here, we further examined the role of intrinsic activity at 5-HT1A receptors in these effects. The anti-cataleptic effects of 5-HT1A receptor ligands with positive intrinsic activity [from high to low: 3-chloro-4-fluorophenyl-(4-fluoro-4-{[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl}-piperidin-1-yl-methanone fumaric acid salt (F 13714), eptapirone, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), 2-[4-[4-(7-methoxy-1-naphtyl) piperazino]butyl]-4-methyl-2H,4H-1,2,4-triazin-3,5-dione maleic acid salt (F 11461), buspirone, 2-[4-[4-(7-benzofuranyl)piperazino]butyl]-4-methyl-2H,4H-1,2,4-triazin-3,5-dione (F 12826), ipsapirone, and (s)-N-tert-butyl-3-(4-(2-methoxyphenyl)piperazine-1-yl)-2-phenylpropanamide hydrochloride (WAY 100135)] and negative intrinsic activity [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide dihydrochloride (WAY 100635)] were examined. Catalepsy was induced by the classical antipsychotic haloperidol (0.63 mg/kg) and measured in the cross-legged position test and in the bar test. All 5-HT1A receptor agonists, except WAY 100135, significantly attenuated the effects of haloperidol in the cross-legged position test. All agonists had similar effects in the bar test, except ipsapirone, which failed to attenuate haloperidol-induced catalepsy. In contrast to the effects observed with the agonists, the inverse agonist WAY 100635 appeared to enhance haloperidol-induced catalepsy in both tests, in agreement with earlier findings. The maximal effects of the 5-HT1A receptor ligands to attenuate catalepsy correlated positively with the rank order of their intrinsic activity at 5-HT1A receptors (either catalepsy test: rS=0.92, P<0.001). F 13714, which had the highest intrinsic activity, maximally inhibited haloperidol-induced catalepsy in the cross-legged position and bar tests (100% and 99% inhibition, respectively). Because the magnitude of the anti-cataleptic effects of 5-HT1A receptor ligands correlates positively with their intrinsic activity, it is likely that F 13714 has marked anti-cataleptic effects because of its high intrinsic activity at 5-HT1A receptors.

Buspirone improves the anti-cataleptic effect of levodopa in 6-hydroxydopamine-lesioned rats

In Parkinson‘s disease (PD), prolonged exposure to L-3,4-dihydroxyphenylalanine (L-DOPA) results in motor fluctuations, such as the on-off phenomenon, and L-DOPA-induced dyskinesia. Previously, we found that activation of 5-HT1A in the substantia nigra pars compacta (SNc) decreased catalepsy in parkinsonian rats. In the current investigation, we attempted to evaluate the effect of buspirone on the anti-cataleptic effect of L-DOPA in 6-hydroxydopamine (6-OHDA)-lesioned male Wistar rats. Catalepsy was induced by the unilateral infusion of 6-OHDA (8μg/2μl/rat) into the central region of the SNc. After a 3-week recovery period, rats received L-DOPA intraperitoneally (ip; 15mg/kg) twice daily for 20 days, and the anti-cataleptic effect of L-DOPA was assessed by the bar test at days 5, 10, 15 and 20. The results showed that L-DOPA had an anti-cataleptic effect only until day 15, and its effect was abolished on day 20. On day 21, these rats were co-treated with three different doses of buspirone (0.1, 0.5 and 2.5mg/kg, ip) and L-DOPA (15mg/kg, ip). At a dose of 0.5mg/kg, buspirone improved the anti-cataleptic effect of L-DOPA. Furthermore, the effect of buspirone (0.5mg/kg, ip) on the anti-cataleptic effect of L-DOPA (15mg/kg, ip) was reversed by 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl)piperazine hydrobromide (NAN-190; 0.5mg/kg, ip), a 5-HT1A receptor antagonist. From these results, it may be concluded that buspirone improves the anti-cataleptic effect of L-DOPA in a 6-OHDA-induced animal model of PD through the activation of 5-HT1A receptors. In this regard, further investigations should be undertaken to clarify the exact mechanism of the interaction between 5-HT1A and dopaminergic neurons.

Antipsychotic-induced catalepsy is attenuated in mice lacking the M4 muscarinic acetylcholine receptor

A delicate balance exists between the central dopaminergic and cholinergic neurotransmitter systems with respect to motor function. An imbalance can result in motor dysfunction as observed in Parkinson's disease patients and in patients treated with antipsychotic compounds. Cholinergic receptor antagonists can alleviate extrapyramidal symptoms in Parkinson's disease and motor side effects induced by antipsychotics. The effects of anticholinergics are mediated by muscarinic receptors of which five subtypes (M1–M5) exist. Muscarinic M4 receptors are found at high concentrations in motor parts of the striatum, suggesting a role for muscarinic M4 receptors in the motor side effects of antipsychotics, and in the alleviation of these side effects by anticholinergics. Here we investigated the potential role of the muscarinic M4 receptor in catalepsy induced by antipsychotics (haloperidol and risperidone) as well as the anti-cataleptic effects of the non-selective anticholinergic drug scopolamine in fully backcrossed muscarinic M4 receptor knockout mice. The drug-induced catalepsy was strongly attenuated, but not abolished, in M4 knockout mice as compared to wild-type controls. Scopolamine further attenuated the cataleptic response in M4 knockout mice, suggesting that non-M4 muscarinic receptors also participate in the anti-cataleptic effects. In conclusion, these data indicate an important role for M4 receptors in antipsychotic-induced motor side effects and suggest that M4 receptors could be a target for future pharmacological treatment of antipsychotic-induced as well as idiopathic parkinsonism.

The role of 5‐HT2A receptor and 5‐HT2A/5‐HT1A receptor interaction in the suppression of catalepsy

In the present study, the 5-HT(2A) and 5-HT(1A) receptors functional activity and 5-HT(2A) receptor gene expression were examined in the brain of ASC/Icg and congenic AKR.CBAD13Mit76C mouse strains (genetically predisposed to catalepsy) in comparison with the parental catalepsy-resistant AKR/J and catalepsy-prone CBA/Lac mouse strains. The significantly reduced 5-HT(2A) receptor functional activity along with decreased 5-HT(2A) receptor gene expression in the frontal cortex was found in all mice predisposed to catalepsy compared with catalepsy-resistant AKR/J. 5-HT(2A) agonist DOI (0.5 and 1 mg/kg, i.p.) significantly reduced catalepsy in ASC/Icg and CBA/Lac, but not in AKR.CBAD13Mit76C mice. Essential increase in 5-HT(1A) receptor functional activity was shown in catalepsy-prone mouse strains in comparison with catalepsy-resistant AKR/J mice. However, in AKR.CBAD13Mit76C mice it was lower than in ASC/Icg and CBA/Lac mice. The inter-relation between 5-HT(2A) and 5-HT(1A) receptors in the regulation of catalepsy was suggested. This suggestion was confirmed by prevention of DOI anticataleptic effect in ASC/Icg and CBA/Lac mice by pretreatment with 5-HT(1A) receptor antagonist p-MPPI (3 mg/kg, i.p.). At the same time, the activation of 5-HT(2A) receptor led to the essential suppression of 5-HT(1A) receptor functional activity, indicating the opposite effect of 5-HT(2A) receptor on pre- and postsynaptic 5-HT(1A) receptors. Thus, 5-HT(2A)/5-HT(1A) receptor interaction in the mechanism of catalepsy suppression in mice was shown.

Evaluation of toxicological and antioxidant potential of Nardostachys jatamansi in reversing haloperidol-induced catalepsy in rats

An aqueous root extract from Nardostachys jatamansi was investigated for its antioxidant and anticataleptic effects in the haloperidol-induced catalepsy rat model of the disease by measuring various behavioral and biochemical parameters. Catalepsy was induced by administration of haloperidol (1 mg/kg, ip) in male albino rats. A significant (P < 0.01) reduction in the cataleptic scores were observed in all the drug-treated groups as compared to the haloperidol-treated group; with maximum reduction observed in the Nardostachys jatamansi (250 and 500 mg/kg body weight) administered group. To estimate biochemical parameters: the generation of thiobarbituric acid reactive substances (TBARS); reduced glutathione (GSH) content and glutathione-dependent enzymes; catalase; and superoxide dismutase (SOD), in the brain were assessed. Haloperidol administration increased generation of TBARS and significantly reduced GSH, which were restored to near normal level with the Nardostachys jatamansi treatment. Catalase and SOD levels were also increased to normal levels, having been reduced significantly by haloperidol administration. Our findings of behavioral studies and biochemical estimations show that Nardostachys jatamansi reversed the haloperidol-induced catalepsy in rats. We conclude that the antioxidant potential has contributed to the reduction in the oxidative stress and catalepsy induced by haloperidol administration.

Effects of substance P in globus pallidus on haloperidol-induced Parkinsonian model rats

To investigate the effects of substance P in globus pallidus on haloperidol-induced Parkinson's disease model rat.Methods In behavioral experiments,guide cannulae constructed from stainless steel were implanted into the globus pallidus.After five days recovery,0.5 μl drugs(normal saline,SMSP,SR140333B,SR140333B + SMSP)were bilaterally microinjected into the globus pallidus in awake rats with haloperidol administration intraperitoneally.The catalepsy was then observed within 60 min.In electrophysiological study,an in vivo extracellular recording was performed to observe the effects of substance P on the firing rate of pallidal neurons.Resuits Haloperidol induced catalepsy in rats with intrapallidal saline microinjection.The maximum average latency was(259.8±34.8)s at the time point of 30th min.The minimum average latency was(145.2±54.8)s at 50th min.Bilateral microinjection of SMSP into globus pallidus significantly attenuated haloperidol-induced catalepsy (The average latency was(10.4±3.4)s at lOth rain and(58.4±38.8)s at 60th min,P＜0.01).This anticataleptic effect was completely counteracted by selective NK-1 receptors antagonist SR140333B(The average latency was(176.4±64.4)s at 10th min and(139.2±59.7)s at 60th rain,P＜0.01).Furthermore,micropressure ejection of SMSP significantly increased the firing rate of pallidal neurons(Basal:(13.4±4.2)Hz,SMSP:(17.5±5.6)Hz).The average increase was(29.4±8.6)%(P＜0.05,n=13).SR140333 B completely blocked SMSPinduced increase in firing rate(SR140333B:(10.3±2.5)Hz,SR140333 B + SMSP:(11.3±3.0)Hz,P＞0.05,n=8).Conclusion Based on the action of substance P in globus pallidus of parkinsonian rats,it is we hypothesized that activation of substance P receptor in globus pallidus may play a role in the treatment of Parkinson's disease. Key words: Globus pallidus; Substance P; Haloperidol; Parkinson's disease

Chronic Actions of Thyroxine on Behavior and Serotonin Receptors in Mouse Strains with Contrasting Predispositions to Catalepsy

The studies reported here addressed the effects of chronic administration of thyroxine (2 mg/liter for 60 days) on catalepsy and the functional activity and expression of the 5-HT(1A) and 5-HT(2A) receptor genes in the brains of adult male mice of the cataleptic ASC strain and the catalepsy-resistant AKR strain. Thyroxine induced cataleptics in AKR mice but had anticataleptic activity in ASC animals. Chronic thyroxine administration increased the functional activity and expression of 5-HT(2A) receptors in the frontal cortex in AKR mice but not in ASC mice. In ASC mice, the hormone significantly weakened the hypothermic effect of the 5-HT(1A) receptor agonist 8-OH-DPAT, though it did not alter the expression of these receptors. These results suggest that 5-HT(2A) receptors are involved in the cataleptogenic while 5-HT(1A) receptors are involved in the anticataleptic effects of the hormone in mice.

Effects of 5-HT in globus pallidus on haloperidol-induced catalepsy in rats

Histological, behavioral and electrophysiological studies have suggested that 5-HT may regulate motor function by affecting globus pallidus neurons activity. In this study, the effects of 5-HT in globus pallidus on haloperidol-induced catalepsy and its possible receptor mechanisms were examined in rats using bar tests. Bilateral microinjection of 5-HT (10 μM) into globus pallidus significantly attenuated haloperidol-induced catalepsy. This anticataleptic effect was completely counteracted by selective 5-HT 1B receptors antagonist SB-224289 (10 μM), while partly reversed by selective 5-HT 4 receptors antagonist GR-113808 (1 μM). In addition, the selective 5-HT 7 receptors antagonist SB-269970 (1 μM) partly reversed the anticataleptic effect of 5-HT only at the incipient period after the intrapallidal injection. In conclusion, 5-HT in globus pallidus could attenuate haloperidol-induced catalepsy via multiple receptor mechanisms.

Glycyrrhiza glabra as an adjuvant in treatment of Parkinsonism and depression

The treatment of Parkinson's disease and depression is still far from satisfactory. The objective of the present study was to evaluate the potential of methanolic extract of Glycyrrhiza glabra (GGE) as an adjuvant in treatment of Parkinson's disease and depression. In acute study GGE (30 and 100mg/kg i.p.) significantly inhibited haloperidol-induced catalepsy in mice in dose dependent manner. Similar inhibitory effect of GGE was also observed in chronic study (15 days) indicating that there was no development of tolerance. The GGE reduced duration of catalepsy also. In mice treated with GGE (30mg/kg i.p.) for 6 days and given haloperidol on 7th day showed significantly (P&lt;0.05) diminished catalepsy and the higher dose completely inhibited catalepsy. This indicated its ability to retain the anticataleptic effect. Further GGE in both the doses increased apomorphine-induced sniffing indicating stimulation of Dopamine D1 receptor stimulation.

Functional interaction between adenosine A2A and group III metabotropic glutamate receptors to reduce parkinsonian symptoms in rats

Non-dopaminergic drugs acting either on adenosine A2A or metabotropic glutamate (mGlu) receptors reduce motor impairment in animal models of Parkinson's disease (PD), suggesting a possible functional interaction between these receptors to regulate basal ganglia function. The present study therefore tested the behavioural effects of compounds acting selectively on A2A or on specific mGlu receptor subtypes, alone or in combination, in rodent models of PD. Acute administration of the adenosine A2A receptor antagonists CSC or MSX-3 at the highest doses tested (5 and 1.25 mg/kg, respectively) significantly reduces haloperidol-induced catalepsy. Furthermore, the anticataleptic effect of MSX-3 was enhanced by a 3-week treatment. Acute administration of the selective group III mGlu agonist ACPT-I produces potent anticataleptic effects and prolongs time on rotarod of 6-OHDA-lesioned rats. In contrast, acute or chronic administration of MPEP (mGlu5 receptor antagonist) has no anticataleptic action. Furthermore, the acute co-administration of ACPT-I 1 mg/kg, but not 5 mg/kg, with CSC markedly reduces catalepsy. Opposite effects are observed after a 3-week co-administration. The co-administration of ACPT-I with MSX-3 has anticataleptic effects both after acute or chronic treatment. In contrast, acute combination of subthreshold doses of CSC and MPEP has no effect. After a 3-week treatment, however, the combination of CSC and MPEP was found to reduce haloperidol-induced catalepsy. Altogether, these results show for the first time that systemic activation of group III mGlu receptors with ACPT-I provides benefits in parkinsonian rats and underlie a possible interaction with A2A receptors to regulate basal ganglia motor function.

Brain Adenosine A2A Receptor Occupancy by a Novel A1/A2A Receptor Antagonist, ASP5854, in Rhesus Monkeys: Relationship to Anticataleptic Effect

The purpose of the present study was to measure adenosine A(2A) receptor (A(2A)R) occupancy in the brain by a novel adenosine A(1)/A(2A) antagonist, 5-[5-amino-3-(4fluorophenyl)pyrazin-2-yl]-1-isopropylpyridine-2(1H)-one (ASP5854), and to determine the degree of receptor occupancy necessary to inhibit haloperidol-induced catalepsy in rhesus monkeys. A(2A)R occupancy by ASP5854 (0.001-0.1 mg/kg) was examined in the striatum using an A(2A)R-specific radiotracer, (11)C-SCH442416, and PET in conscious rhesus monkeys. A(2A)R occupancy was monitored after a single intravenous administration of ASP5854 in 3 animals, and a dynamic PET scan was performed at 1, 4, and 8 h after an intravenous bolus injection of the tracer for approximately 740 MBq. Catalepsy was induced by haloperidol (0.03 mg/kg, intramuscularly) and examined for incidence and duration. ASP5854 dose-dependently increased A(2A)R occupancy in the striatum and showed long-lasting occupancy even after the reduction of plasma concentration. Haloperidol induced severe catalepsy at 40 min after intramuscular injection. The incidence and duration of cataleptic posture were dose-dependently reduced by ASP5854 at 1 h after oral administration, and the minimum ED(50) value was 0.1 mg/kg. Administration of a dose of 0.1 mg/kg yielded a plasma concentration of 97 +/- 16.3 ng/mL, which corresponded to 85%-90% of A(2A)R occupancy. These results showed that ASP5854 antagonized A(2A)R in the striatum, and the dissociation from A(2A)R was relatively slow. In addition, more than 85% A(2A)R occupancy by ASP5854 resulted in an inhibition of haloperidol-induced catalepsy. Thus, such a pharmacodynamic study directly demonstrates both the kinetics of a drug in the brain and the relationship between dose-dependent receptor occupancy and plasma level.

Effect of Withania somnifera root extract on haloperidol‐induced catalepsy in albino mice

The objective of the study was to evaluate the anticataleptic effect of Withania somnifera (WS) extract, on haloperidol-induced catalepsy in albino mice. Catalepsy was induced with haloperidol (1 mg/kg) i.p. in five groups of male albino mice (n = 6). Three groups received Withania somnifera extract (1.7, 4.25, 8.5 mg/kg) respectively, one group received scopolamine (1 mg/kg) and one group received the vehicle (1% gum acacia) orally, 30 min prior to haloperidol administration. Catalepsy was measured by using standard bar test at 30, 60, 90, 120 and 240 min. This constituted the acute study. For the chronic study, the drugs were administered for 6 more days. Catalepsy was again measured on day 7. Animals were then sacrificed by cervical dislocation and superoxide dismutase (SOD) activity was estimated in the brain. In this study, Withania somnifera extract treated groups showed a dose dependent reduction in cataleptic scores, both in the acute and chronic study. The SOD activity in brain was also found to be lowered in the WS (4.25 mg, 8.5 mg/kg) treated groups. In conclusion, Withania somnifera was found to be more efficacious than scopolamine in reversing haloperidol induced catalepsy. A clear correlation between the SOD levels and cataleptic scores was observed. We believe that the antioxidant properties of this drug could have contributed to the anticataleptic effect.

The influence of group III metabotropic glutamate receptor stimulation by (1S,3R,4S)-1-aminocyclo-pentane-1,3,4-tricarboxylic acid on the parkinsonian-like akinesia and striatal proenkephalin and prodynorphin mRNA expression in rats

Group III metabotropic glutamate receptors (mGluRs) are widely distributed in the basal ganglia, especially on the terminals of pathways which seem to be overactive in Parkinson’s disease. The aim of the present study was to determine whether (1 S,3 R,4 S)-1-aminocyclo-pentane-1,3,4-tricarboxylic acid (ACPT-1), an agonist of group III mGluRs, injected bilaterally into the globus pallidus (GP), striatum or substantia nigra pars reticulata (SNr), can attenuate the haloperidol-induced catalepsy in rats, and whether that effect was related to modulation of proenkephalin (PENK) or prodynorphin (PDYN) mRNA expression in the striatum. Administration of ACPT-1 (0.05–1.6 μg/0.5 μl/side) caused a dose-and-structure-dependent decrease in the haloperidol (0.5 mg/kg i.p. or 1.5 mg/kg s.c.)-induced catalepsy whose order was as follows: GP>striatum>SNr. ACPT-1, given alone to any of those structures, induced no catalepsy in rats. Haloperidol (3×1.5 mg/kg s.c.) significantly increased PENK mRNA expression in the striatum, while PDYN mRNA levels were not affected by that treatment. ACPT-1 (3×1.6 μg/0.5 μl/side) injected into the striatum significantly attenuated the haloperidol-increased PENK mRNA expression, whereas administration of that compound into the GP or SNr did not influence the haloperidol-increased striatal PENK mRNA levels. Our results demonstrate that stimulation of group III mGluRs in the striatum, GP or SNr exerts antiparkinsonian-like effects in rats. The anticataleptic effect of intrastriatally injected ACPT-1 seems to correlate with diminished striatal PENK mRNA expression. However, since the anticataleptic effect produced by intrapallidal and intranigral injection of ACPT-1 is not related to a simultaneous decrease in striatal PENK mRNA levels, it is likely that a decrease in enkephalin biosynthesis is not a necessary condition to obtain an antiparkinsonian effect.

Changes in sleep electroencephalogram and nocturnal hormone secretion after administration of the antidyskinetic agent sarizotan in healthy young male volunteers

Sarizotan is a 5-HT(1A) agonist with high affinity to D(3) and D(4) receptors. In animal experiments, the drug shows a strong anti-cataleptic effect and suppresses effectively dyskinesias in animal models of L: -dopa-induced dyskinesia and of tardive dyskinesia. Data from an open pilot study in patients with Parkinson's disease show clear indication of a treatment effect against L: -dopa-induced dyskinesia. CNS-active drugs are known to modulate sleep electroencephalogram (EEG) and sleep-related hormone secretion. 5-HT(1A) agonists suppress rapid-eye movement (REM) sleep and enhance the secretion of ACTH, cortisol, prolactin and growth hormone (GH) at daytime. We hypothesised that sarizotan shares these effects. Furthermore, we were interested in the influence of sarizotan on leptin, which participates in the regulation of the energy balance and is enhanced after various psychoactive drugs. Ten healthy male subjects were investigated twice in a double-blind, placebo-controlled crossover design. Sleep EEG and nocturnal hormone secretion of ACTH, cortisol, prolactin, GH and leptin were examined after oral administration of either placebo or 20 mg of sarizotan at night. After administration of sarizotan, a significant reduction of REM sleep and total sleep time in conventional sleep EEG and a significant reduction of sigma- and theta-power in spectral analysis were observed. The main effect on nocturnal hormone secretion was a significant elevation of prolactin and of ACTH in the first half of the night. While REM sleep was suppressed, the endocrine effects of 20 mg sarizotan at night were weak. Its sleep-endocrine profile is comparable to the effects provoked by selective 5-HT reuptake inhibitors.

The effect of a 5-HT1A receptor agonist on striatal dopamine release

5-HT1A receptor agonists consistently reduce neuroleptic induced catalepsy in rats. A serotonin-dopamine interaction has been proposed to underlie this effect. Specifically, 5-HT1A receptor agonists may reduce the activity of serotonergic projections that inhibit dopaminergic nigrostriatal neurones, therefore increasing dorsal striatal dopamine levels and partially overcoming the neuroleptic blockade of D2 receptors. We tested the hypothesis that 5-HT1A receptor agonists increase striatal dopamine release in man using PET scanning with the selective D2 receptor radioligand [11C]raclopride, which is sensitive to endogenous dopamine levels. Six healthy volunteers received two PET scans, one after placebo, the other after 1 mg flesinoxan, a selective 5-HT1A receptor agonist. Binding potential values for striatal subdivisions were determined using a simplified reference tissue model. We did not find any difference in striatal [11C]raclopride binding between conditions, even though flesinoxan lead to typical 5-HT1A receptor agonist side effects and produced elevation of growth hormone in five of the six subjects. Our results suggest that the anticataleptic effect of 5-HT1A receptor agonists is not mediated by striatal dopamine release, and indicates a need for further research with other suitable 5-HT1A receptor agonists.

Anticataleptic properties of alpha2 adrenergic antagonists in the crossed leg position and bar tests: differential mediation by 5-HT1A receptor activation.

Recent studies suggest that alpha(2) adrenoceptor blockade may improve the antipsychotic-like effects of neuroleptics and attenuate dopamine D(2) receptor antagonist-induced catalepsy. However, several alpha(2) adrenergic antagonists also display serotonin 5-HT(1A) receptor agonist activity, which may contribute to anticataleptic actions. In this study, we examined a series of alpha(2) adrenergic antagonists to determine the role of activity at serotonin 5-HT(1A) receptors in their anticataleptic effects. Catalepsy in rats induced by the antipsychotic haloperidol (2.5 mg/kg, SC) was measured using the cross-legged position (CLP) and bar tests. The compounds examined in this study, in decreasing rank order of alpha(2) adrenergic versus 5-HT(1A) receptor selectivity, were atipamezole, methoxy-idazoxan (RX821002), efaroxan, idazoxan, and yohimbine. Antagonism studies were conducted using the selective 5-HT(1A) receptor antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide dihydrochloride (WAY100635). Idazoxan, efaroxan, and yohimbine significantly attenuated the cataleptic effects of haloperidol (2.5 mg/kg, SC) in the CLP test and the actions of their highest doses were significantly blocked by pre-treatment with WAY100635 (0.63 mg/kg, SC). In contrast to the other compounds, methoxy-idazoxan was ineffective in the CLP test. Atipamezole exhibited anticataleptic effects in the bar and CLP tests which were not blocked by WAY100635. Similarly, the anticataleptic effects of methoxy-idazoxan and idazoxan in the bar test were not blocked by WAY100635. Serotonin 5-HT(1A) receptors play a prominent role in anticataleptic effects of certain alpha(2) adrenergic antagonists in the CLP test, whereas alpha(2)-adrenergic mechanisms are likely to be primarily responsible for the anticataleptic effects of these ligands in the bar test.