Experimental treatment of antipsychotic-induced movement disorders

Antipsychotic drugs are extensively prescribed for the treatment of schizophrenia and other related psychiatric disorders. These drugs produced their action by blocking dopamine (DA) receptors, and these receptors are widely present throughout the brain. Therefore, extended antipsychotic use also leads to severe extrapyramidal side effects. The short-term effects include parkinsonism and the later appearing tardive dyskinesia. Currently available treatments for these disorders are mostly symptomatic and insufficient, and are often linked with a number of detrimental side effects. Antipsychotic-drug-induced tardive dyskinesia prompted researchers to explore novel drugs with fewer undesirable extrapyramidal side effects. Preclinical studies suggest a role of 5-hydroxytryptamine (serotonin)-1A and 2A/2C receptors in the modulation of dopaminergic neurotransmission and motivating a search for better therapeutic strategies for schizophrenia and related disorders. In addition, adjunctive treatment with antioxidants such as vitamin E, red rice bran oil, and curcumin in the early phases of illness may prevent additional oxidative injury, and thus improve and prevent further possible worsening of related neurological and behavioral deficits in schizophrenia. This review explains the role of serotonergic receptors and oxidative stress, with the aim of providing principles for prospect development of compounds to improve therapeutic effects of antischizophrenic drugs.

Effects of sugar rich diet on brain serotonin, hyperphagia and anxiety in animal model of both genders

Lower levels of 5-hydroxytryptamine (5-HT; serotonin) in the brain elicit sugar craving, while ingestion of sugar rich diet improves mood and alleviates anxiety. Gender differences occur not only in brain serotonin metabolism but also in a serotonin mediated functional responses. The present study was therefore designed to investigate gender related differences on the effects of long term consumption of sugar rich diet on the metabolism of serotonin in the hypothalamus and whole brain which may be relevant with the hyperphagic and anxiety reducing effects of sugar rich diet. Male and female rats were fed freely on a sugar rich diet for five weeks. Hyperphagic effects were monitored by measuring total food intake and body weights changes during the intervention. Anxiolytic effects of sugar rich diet was monitored in light-dark transition test. The results show that ingestion of sugar rich diet decreased serotonin metabolism more in female than male rats. Anxiolytic effects were elicited only in male rats. Hyperphagia was comparable in both male and female rats. Finings would help in understanding the role of sugar rich diet-induced greater decreases of serotonin in sweet craving in women during stress.

Reversal of haloperidol induced motor deficits in rats exposed to repeated immobilization stress

Stress is defined as a non specific response of body to any physiological and psychological demand. Preclinical studies have shown that an uncontrollable stress condition produces neurochemical and behavioral deficits. The present study was conducted to test the hypothesis that a decrease in the responsiveness of somatodendritic 5-hydroxytryptamine (5-HT)-1A receptors following adaptation to stress could attenuate haloperidol induced acute parkinsonian like effect. Results showed that single exposure (2h) to immobilization stress markedly decreased food intake, growth rate and locomotor activity but these stress-induced behavioral deficits were not observed following repeated (2h/day for 5 days) exposure of immobilization stress suggesting behavioral tolerance occurs to similar stress. An important finding of present study is a reversal of haloperidol-induced motor deficits in animals exposed to repeated immobilization stress than respective control animals. It is suggested that stress induced possible desensitization of somatodendritic 5-HT-1A as well as 5-HT-2C receptors could release dopamine system from the inhibitory influence of serotonin. On the other hand, an increase in the effectiveness of postsynaptic 5-HT-1A receptors elicits a direct stimulatory influence on the activity of dopaminergic neuron and is possibly involved in the reversal of haloperidol-induced parkinsonian like symptoms in repeatedly immobilized rats.

Oral administration of haloperidol at clinically recommended doses elicits smaller parkinsonian effects but more tardive dyskinesia in rats

The present study was designed to monitor extrapyramidal symptoms (EPS) elicited by the oral administration of haloperidol at clinically recommended doses and to compare it with EPS produced when the drug is injected intraperitoneally at doses used in animal research. Rats injected with haloperidol at a dose of 1 mg/kg daily for 5 weeks exhibited akinesia in an open field and impaired motor coordination. Effects of the drug on motor coordination but not on open field akinesia were attenuated gradually from 2-5 weeks of treatment. Oral administration of haloperidol in drinking water at clinically recommended dose exhibited decreased exploratory activity without producing akinesia. Motor coordination was impaired maximally after 3 weeks and tolerance was developed in the drug induced motor impairment after 5 weeks of treatment. Intensity of vacuous chewing movements (VCMs) and tardive VCMs was greater by oral administration than intraperitoneal injections of haloperidol. The present results showed that oral administration of haloperidol expected to produce sustained effect may result in tolerance in acute parkinsonian like effects but more intensity of tardive dyskinesia. We suggest that drugs which may helpful in alleviating tardive dyskinesia may be more useful if person is on oral drug therapy.

Perception of academic examination stress: effects on serum leptin, cortisol, appetite and performance

BACKGROUND

Examination stress is a psychological stress that activate hypothalamic-pituitary adrenocortical (HPA) axis to increase circulating levels of glucocorticoids. The fat derived hormone leptin is also released in response to stress-inducing condition. To workout the role of leptin and cortisol in response to perceived levels of examination stress and their effects on academic performance. The present study was designed to monitor the relationship of self reported perceived levels of examination stress on serum levels of cortisol and leptin in female students going to appear in university examination.

METHODS

Fifty-six female undergraduate students participated in the study. Examination stress, appetite levels were assessed by a questionnaire and blood samples were collected one hour before appearing in the examination. Performance was evaluated from the marks obtained in that particular examination.

RESULTS

Serum cortisol levels increased with an increase in the intensity of perceived examination stress. Serum leptin levels increased only in the group under moderate stress while increases in mild and severe stress group were not significant. Mild to moderate stress enhanced performance but severe stress decreased it.

CONCLUSIONS

The present study shows an inverted U-shaped relationship between self reported different levels of perceived examination stress and academic performance.

Reversal of haloperidol-induced motor deficits by mianserin and mesulergine in rats

Although haloperidol is widely prescribed for the treatment of schizophrenia, its beneficial effects are accompanied by extrapyramidal side effects (EPS). Role of 5-HT-2A/2C receptors in the attenuation of acute Parkinsonian-like effects of typical antipsychotics is investigated by prior administration of mianserin and mesulergine to rats injected with haloperidol. In the first part of study effects of various doses of haloperidol (0.5, 1.0, 2.5 and 5.0 mg/kg) were determined on motor activity and a selected dose (1 mg/kg) was used to monitor attenuation of parkinsonian effects by two different doses of 5-HT-2A/2C receptor antagonists mianserin (2.5 & 5.0 mg/kg) and mesulergine (1.0 & 3.0 mg/kg). Rats treated with haloperidol at doses of 0.5-5.0 mg/kg exhibited impaired motor coordination and a decrease in exploratory activity in an open field. The dose response curve showed that at a dose of 1 mg/kg significant and submaximal effects are produced on motor coordination and exploratory activity. Coadministration of mianserin and mesulergine attenuated and reversed haloperidol-induced motor deficits in a dose dependent manner. The mechanism involved in the attenuation / reversal of haloperidol-induced parkinsonian like symptoms by mianserin and mesulergine is discussed. Prior administration of mianserin or mesulergine may be of use in the alleviation of EPS induced by conventional antipsychotic drugs.The findings have potential implication in the treatment of schizophrenia and motor disorders.

Motor effects of buspirone: Relationship with dopamine and serotonin in the striatum

OBJECTIVE

To determine the effect of low and high doses of buspirone on motor activity and striatal monoamine metabolism in rats.

DESIGN

Experimental study.

PLACE AND DURATION OF STUDY

The experiments were performed in the Department of Biochemistry, Karachi University from October to December 2003.

SUBJECTS AND METHOD

Behavioral and neurochemical effects of agents were monitored acutely. Motor activity was scored in open field. Neurochemical estimations in the striatum were carried out by high performance liquid chromatography.

RESULTS

Administration of buspirone at low (1 mg/kg) and high (10 mg/kg) doses increased latency to move in open field and decreased number of squares crossed. The agent injected at a dose of 1 mg/kg decreased dopamine concentration and increased the concentration of homovanillic acid. Increases of homovanillic acid were smaller at a dose of 1 mg/kg than 10 mg/kg. Changes in the levels of dihydroxyphenyl acetic acid were not significant. Administration of buspirone decreased 5-hydroxytryptamine metabolism at a dose of 1 mg/kg but not at a dose of 10 mg/kg.

CONCLUSION

The present results provide neurochemical evidence that low but not high dose of buspirone preferentially stimulates somatodendritic 5-hydroxytryptamine-1A receptors resulting in a decrease in striatal serotonin metabolism. Low dose of buspirone could release dopaminergic neurons from inhibitory influence of serotonin and may be useful in reducing parkinsonian-like effects of traditional antipsychotics.

Dopamine and serotonin neurotransmission in the reinforcing effects of alcohol and apomorphine

OBJECTIVE

To determine the role of dopamine and 5-hydroxytryptamine (5-HT; serotonin) in the reinforcing effects of alcohol and apomorphine.

DESIGN

Experimental study.

PLACE AND DURATION OF STUDY

Department of Biochemistry, University of Karachi from September to November 2004.

SUBJECTS AND METHODS

The study was conducted on 24 male albino Wistar rats. Reinforcing effects were monitored in a conditioned place preference (CPP) paradigm using a light-dark activity box. Slicing and punching method was used to collect dorsal and ventral striatum. Neurochemical estimations were done by HPLC-EC.

RESULTS

Withdrawal from repeated administration of ethanol (1g/kg/day) as well as apomorphine (1 mg/kg/day) elicited reinforcement that could be monitored in a CPP paradigm. CNS depressant effects of ethanol were not altered on repeated administration but CNS stimulatory effects of apomorphine increased. Reinforcing effects of ethanol but not apomorphine were associated with a decrease in dopamine metabolism in the ventral striatum.

CONCLUSION

A decrease in the activity of dopaminergic neurons following withdrawal from repeated administration is involved in the compulsive use of abused drugs.

Somatodendritic and postsynaptic serotonin-1A receptors in the attenuation of haloperidol-induced catalepsy

The mechanism by which stimulation of somatodendritic and/or postsynaptic 5-hydroxytryptamine (5-HT, serotonin)-1A receptor could attenuate acute Parkinsonian-like effects of typical antipsychotics is investigated by comparing the anticataleptic and neurochemical effects of 8-hydroxy-2-di-n-propylaminotetralin (8-OH-DPAT) and buspirone in rats injected with haloperidol. Cataleptic effects of a submaximal dose (1 mg/kg) of haloperidol were attenuated more by prior administration of 8-OH-DPAT (0.25 mg/kg) than buspirone (1 mg/kg). Striatal 5-HT metabolism decreased more in buspirone- than 8-OH-DPAT-injected animals. Administration of haloperidol did not alter 5-HT metabolism in saline-, 8-OH-DPAT- or buspirone-injected animals. Dopamine decreased and its metabolite homovanillic acid (HVA) increased in the striatum of rats injected with buspirone. Effects of 8-OH-DPAT on dopamine metabolism were not significant. Haloperidol-induced increases of dopamine metabolites were attenuated by prior administration of 8-OH-DPAT, but not buspirone. The mechanism by which stimulation of somatodendritic as well as postsynaptic 5-HT-1A receptors could attenuate haloperidol-induced catalepsy is discussed. The findings have potential implications in the treatment of schizophrenia and motor behavior.

Neurochemical effects of 8-hydroxy-2-di-n-propylamino tetralin in rats treated with haloperidol

In view of a possible role of presynaptic serotonin (5-hydroxytryptamine, 5-HT) receptors in the precipitation of extrapyramidal side effects (EPS), the present study was designed to investigate the neurochemical effects of a selective 5-HT1A ligand, 8-hydroxy-2- (di-n-propylamino) tetralin (8-OH-DPAT) in rats following single (5 mg/kg) and repeated (two-times a day for 9 days at dosage of 5mg/kg) haloperidol administration. Haloperidol plus 8-OH-DPAT injected animals exhibited a decrease in dopamine (DA) and an increase in DA metabolite homovanillic acid (HVA) levels in the striatum and rest of the brain. The two groups of animals exhibited comparable levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the striatum and rest of the brain. Animals injected with haloperidol and killed 24 hrs after the last injection of haloperidol exhibited higher DA and HVA levels in the striatum but not in the rest of the brain. Conversely, dihydroxyphenylacetic acid (DOPAC), the other metabolite of DA, decreased in the rest of the brain. 5-HIAA concentrations increased in the striatum but not in the rest of the brain. Administration of 8-OH-DPAT significantly decreased 5-HT and 5-HIAA levels in the rest of brain and did not alter 5-HIAA in the striatum of repeated saline injected rats. Conversely, same dose of 8-OH-DPAT injected to repeatedly haloperidol injected animals did not decrease 5-HT and 5-HIAA concentrations in the rest of the brain but decreased 5-HIAA levels in the striatum. No effect of 8-OH-DPAT injections occurred on striatal or rest of the brain DA metabolism in repeatedly saline injected animals except that DOPAC decreased in the striatum of both groups. The results are discussed in the context of a role of somatodendritic 5-HT1A receptors in the regulation of DA metabolism following single and repeated administration of haloperidol. It is suggested that an increase in the responsiveness of these receptors may be involved in the precipitation of EPS observed in patients on haloperidol therapy.