Neurochemical and some related psychopharmacological aspects of Tourette's syndrome: an update

Effects of donepezil, nicotine and haloperidol on the central serotonergic system in mice: implications for Tourette's syndrome

We have previously reported that acute and chronic donepezil and nicotine administration significantly attenuate DOI-induced head twitch response (HTR) in mice. This behavior, primarily mediated by stimulation of 5-HT2A receptors, has been proposed to model tic symptoms seen in Tourette's syndrome (TS). Haloperidol, a drug widely used to treat symptoms of TS, has also been reported to reduce DOI-induced head shakes in rodents when administered acutely. These findings suggest an inhibitory interaction of these drugs with 5-HT2A receptors. To test this hypothesis, we evaluated the effects of chronic donepezil, nicotine and haloperidol on expression levels of 5-HT2A mRNA and 5-HT2A receptor density in select brain regions. Initially, we established a dose-response relationship for the acute and chronic haloperidol and DOI-induced HTR. Male ICR mice were treated twice daily with donepezil (0.1 mg/kg), nicotine (0.5 mg/kg), and once daily with haloperidol (0.4 mg/kg) for 14 days and were sacrificed 16-18 h after the last injection. These drug regimens were chosen because of their significant effects on DOI-induced HTR. Donepezil significantly increased 5-HT2A mRNA level, but not the receptor density in the striatum. In the midbrain, donepezil significantly decreased the receptor density without affecting the 5-HT2A mRNA level. In the frontal cortex, only haloperidol significantly reduced the 5-HT2A receptor density. The cortex was the only area where donepezil, nicotine and haloperidol significantly reduced the 5-HT2A receptor density. The results suggest that the anti-tic properties of donepezil, nicotine and haloperidol in this paradigm might be due to antagonism of cortical 5-HT2A receptors. Thus, further investigation of involvement of cortical 5-HT2A receptors in TS as well as evaluation of selective 5-HT2A receptor antagonists in this disorder is warranted.

Effects of donepezil on DOI-induced head twitch response in mice: implications for tourette syndrome

Tourette syndrome (TS) is a neurological disorder characterized by persistent motor and phonic tics. Administration of the selective 5-HT(2A/2C) agonist 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) induces head twitches in mice that have been proposed to model tics seen in TS. Previous studies have demonstrated that nicotine markedly attenuates DOI-induced head twitch response (HTR). This and the reports that nicotine may have clinical efficacy in reducing symptoms of TS suggest possible involvement of the nicotinic cholinergic system in this disorder. Donepezil is an acetylcholinesterase inhibitor approved for use in mild to moderate Alzheimer's disease. The purpose of this study was to investigate whether donepezil might also reduce DOI-induced HTR, and whether its combination with nicotine might result in an additive or synergistic effect. Moreover, to elucidate the possible role of nicotinic receptors in this paradigm, the effects of mecamylamine, a nicotinic antagonist, was also evaluated. Acute and chronic administration of donepezil (0.1 mg/kg) or nicotine (0.5 mg/kg base), significantly reduced DOI-induced HTR. No additive or synergistic effects of donepezil and nicotine were observed. Acute mecamylamine administration (0.5-5.0 mg/kg) dose-dependently inhibited DOI-induced HTR. None of the mecamylamine doses blocked the inhibitory effects of donepezil or nicotine on DOI-induced HTR. These results suggest that donepezil may have therapeutic potential in treating motor tic symptoms of TS. Moreover, the action of donepezil and nicotine may be mediated through the same mechanism.

Risperidone in the treatment of tourette syndrome: a double-blind, placebo-controlled trial

A double-blind, placebo-controlled trial was performed to determine the efficacy and tolerability of 8 weeks of treatment with risperidone in the management of 48 adolescent and adult patients with Tourette syndrome. Twenty-four patients were randomly assigned to treatment with risperidone in doses of 0.5 to 6.0 mg/day, and 24 were assigned to placebo. The dosage of medication was increased in fixed increments during the first week of double-blind treatment and thereafter in a flexible dose regimen according to clinical response. Risperidone, at a median dose of 2.5 mg/day (range, 1 to 6 mg/day), was found to be significantly ( p < 0.05) superior to placebo on the Global Severity Rating of the Tourette Syndrome Severity Scale. The proportion of patients who improved by at least one point on this seven-point scale was 60.8% in the risperidone group and 26.1% in the placebo group. Treatment with risperidone was accompanied by an improvement in global functioning in patients with average to above-average impairment at baseline as measured by the Global Assessment of Functioning scale. With respect to extrapyramidal symptom scores measured on the Extrapyramidal Symptom Rating Scale, hypokinesia and tremor increased in the risperidone group, but the effect on tremor was largely confined to subjects with higher baseline tremor scores. There were no significant differences in dystonic reactions, dyskinetic movements, subjective parkinsonism, or akathisia. Risperidone did not increase obsessive-compulsive symptoms. Fatigue and somnolence were the most common adverse events associated with risperidone.

Nicotine attenuates DOI-induced head-twitch response in mice: implications for Tourette syndrome

Tourette syndrome (TS), a chronic neuropsychiatric disorder, is characterized by motor and vocal tics. Preliminary clinical studies indicate possible therapeutic benefits of nicotine in the treatment of Tourette's syndrome (TS). It has been proposed that twitches of the head in mice or twitches of head and shoulders in rats following administration of the selective 5HT(2A/C) agonist DOI (1-)2,5-dimethoxy-4-iodophenyl-2-aminopropane, can serve as an animal model of tics in TS. In this study, the effects of acute and chronic administration of nicotine on DOI-induced head twitch response (HTR) in male albino ICR mice were evaluated. Both acute and chronic nicotine (daily injections for 10 days) reduced the DOI-induced HTR. Moreover, chronic administration of DOI (1 mg/kg/day for 10 days) resulted in 65% increase in [125I]alpha-bungarotoxin binding in cerebellum and 41% increase in striatal [3H]cytisine binding. However, the acute inhibitory effects of nicotine were not blocked by pretreatment with the nicotinic antagonist, mecamylamine. Indeed, at higher doses, mecamylamine also reduced the DOI-induced HTR. The data suggest that both nicotine and mecamylamine may be of therapeutic potential in the treatment of some symptoms of TS.

Tics and its disorders

Tourette syndrome (TS) is familial neuropsychiatric disorder that is characterized by motor and phonic tics that begin in childhood. Once thought of as a rare and debilitating disorder, in the last decade new scientific knowledge suggests that TS and related tic disorders are more common and less debilitating for the majority of individuals. Evidence points toward a spectrum of TS symptomatology that extends beyond the tics disorder to probably include obsessive-compulsive disorder, attention deficit hyperactivity disorder, and mood disorders. Tourette syndrome and its differential diagnosis are discussed in this article with a focus on new developments in classification, etiology, epidemiology, genetics, pathophysiology, and clinical management.

Postprandial changes in superoxide dismutase activity in subjects with Gilles de la Tourette syndrome and controls

Erythrocyte measures of copper-zinc superoxide dismutase (CuZnSOD) were performed on 11 subjects with a clinical diagnosis of Gilles de la Tourette syndrome (GTS) and 6 healthy controls at specified intervals throughout the day. There were no significant differences between GTS subjects and controls but in both subjects and controls there was a significant increase in SOD, 75 min postprandially, which decreased to baseline 135 min postprandially. This has implications for the timing of biological samples in future studies of SOD. Possible reasons for the increase are discussed.

Risperidone in the treatment of Tourette syndrome: a retrospective case note study

Nineteen patients with Tourette syndrome (TS) were treated with risperidone, at a mean daily dose of 1.5 mg. Of those, 41% responded positively, 35% felt that it had made no difference, while it made 24% worse. Although 53% of the patients experienced side-effects, none had extrapyramidal side-effects. At follow-up, 8 to 11 months later, only two of 19 (11 %) patients were still taking risperidone. We suggest that risperidone does have a role in a minority of TS sufferers but it is not suggested as the first line treatment. More placebo-controlled studies using risperidone are clearly indicated.

Endogenous opiates: 1995

This article is the eighteenth installment of our annual review of research concerning the opiate system. It includes articles published during 1995 reporting the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects. The specific topics covered this year include stress: tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.