Validation of the tremulous jaw movement model for assessment of the motor effects of typical and atypical antipychotics: effects of pimozide (Orap) in rats

Drug-induced tremulous jaw movements (TJMs) in rats have been used as a model of parkinsonian tremor. Previous studies demonstrated that the typical antipsychotic haloperidol induced TJMs after acute or subchronic administration, while atypical antipsychotics did not. Moreover, it has been suggested that the relative potency for suppression of tacrine-induced TJMs relative to the suppression of lever pressing can be used to discriminate between typical and atypical antipsychotics. In order to validate this model with additional drugs, the present studies assessed the effects of the typical antipsychotic pimozide. In the first series of experiments, the effects of acute pimozide on tacrine-induced TJMs and lever pressing were examined. As with haloperidol, pimozide failed to suppress tacrine-induced TJMs, even at doses considerably higher than those that suppressed lever pressing. In the second group of experiments, rats were given single daily injections of pimozide (0.125-1.0 mg/kg) or tartaric acid vehicle for 13 days, and were observed for TJMs on days 1, 7, and 13. Pimozide induced TJMs in a dose-related manner on all days. The jaw movements occurred largely in the 3-7 Hz frequency range characteristic of parkinsonian tremor. These data support the hypothesis that typical antipsychotics can induce TJMs in rats, and demonstrate that chronic administration of typical antipsychotics is not necessary for induction of TJMs. TJMs induced by acute or subchronic pimozide may be related to early-onset motor syndromes such as drug-induced parkinsonism.

Effects of dehydroepiandrosterone and other sex steroid hormones on mammary carcinogenesis by direct injection of 7,12-dimethylbenz(a) anthracene (DMBA) in hyperprolactinemic female rats

The present study was performed to investigate the effects of dehydroepiandrosterone (DHEA) compared with those of sex steroid hormones on the mammary tumor induced by local injection of 7,12-dimethylbenz(a) anthracene (DMBA) in hyperprolactinemic female rats. Under sustained hyperprolactinemia induced by pimozide (PMZ) from day 21, DMBA was injected locally into the mammary glandular tissues on day 73. Rats were divided into 5 groups as follows; steroid free (DP group), 17 beta-estradiol (DP + E2 group), testosterone (DP + T group), progesterone (DP + Prog group), or dehydroepiandrosterone (DP + DHA group). The growth pattern and histological classification of the tumor in these 5 groups and rats treated only with DMBA (D group) were examined. All of the tumors grew to a size of 10 mm in diameter and after retaining the size for a certain duration, increased the size rapidly again (onset of rapid tumor growth). The period from the day of DMBA administration to that of onset of the rapid tumor growth in DP group was shorter than in D group, and the period in DP + DHA was longer than DP group and longest in steroid-treated groups. The incidence of adenocarcinoma was 2 tumors/16 animals in D group, 9/11 in DP group, 5/11 in DP + Prog group, 2/7 in DP + E2 group, 2/8 in DP + T group, and 0/10 in DP + DHA group. The incidence of adenocarcinoma in each steroid group except in DP + Prog group was lower than in DP group. These results suggest that prolactin (PRL) increases the incidence of adenocarcinoma in the DMBA-induced mammary tumor model, and DHEA especially decreases the incidence of adenocarcinoma.

Pimozide: a review of its pharmacological properties and therapeutic uses in psychiatry

Pimozide 1-(1-[4,4-bis(4-fluorophenyl)butyl]-4-peperidinyl)-2-benzimidazolone, is the first of a new series of psychotropic drugs, the kiphenylbutylpiperidines. It is advocated for once-daily use as maintenance therapy in chronic schizophrenia and for the treatment of psychic and functional disorders induced by personality traits. Published data suggest that in chronic schizophrenia, pimozide 4 to 6mg daily is indistinguishable from maintenance doses of chlorpromazine, fluphenazine, flupenthixol, perphenazine, or thioidazine. Patient groups have usually been to small to allow statistically significant differences to be apparent, but in some trials pimozide was significantly superior to trifluoperzine and to haloperidol. On present evidence, pimozide has no place in the hyperactive, aggressive type of patient or in treating the acute phase of schizophrenia, probably because of its relative lack of sedative properties compared with many antipsychotic drugs. The incidence and severity of extrapyramidal reactions with pimozide are low, but suitably designed controlled studies are needed to determine whether its use leads to a reduction in the requirement for antiparkinsonian medication. In anxious patients, pimozide seems to offer no advantages over currently available anxiolytic agents, either in terms of efficacy or incidence of side-effects. Claims for a specific effect against anxiety associated with psychosis or disturbed personality traits remain unproven.