1. ¹Division of Neurobiology 2, Centre de Recherche Pierre Fabre, Castres, France
2. ²Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA

Correspondence: Dr L Bardin, Division of Neurobiology 2, Centre de Recherche Pierre Fabre, 17 Avenue Jean Moulin, 81106 Castres, France. Tel: +33 56371 4216; Fax: +33 56371 4363; E-mail: laurent.bardin@pierre-fabre.com

Received 25 April 2005; Revised 2 September 2005; Accepted 8 September 2005; Published online 19 October 2005.

Abstract

A new generation of proven or potential antipsychotics, including aripiprazole, bifeprunox, SSR181507 and SLV313, exhibit agonist actions at serotonin 5-HT_1A receptors, but little comparative data are available on their pharmacological profiles. Here, we compared in mice the in vivo antipsychotic-like vs cataleptogenic activities of these compounds with those of drugs that exhibit little interaction at 5-HT_1A receptors, such as haloperidol, olanzapine and risperidone. All the drugs dose-dependently reduced apomorphine-induced climbing or sniffing and, with the exception of ziprasidone, produced complete suppression of these responses. In the bar catalepsy test, when administered alone, haloperidol, olanzapine and risperidone produced marked catalepsy, whereas, at doses up to 40 mg/kg, aripiprazole, SLV313, SSR181507, and sarizotan produced little or no catalepsy. The latter compounds, therefore, displayed a large separation between doses with 'antipsychotic-like' and those with cataleptogenic actions. When 5-HT_1A receptors were blocked by pretreatment with WAY100635 (2.5 mg/kg, s.c.), cataleptogenic properties of SSR181507 and sarizotan were unmasked, and the catalepsy induced by bifeprunox was enhanced. In the case of aripiprazole and SLV313, although WAY100635 produced upward shifts in their dose–response, the magnitude of catalepsy appeared to reach an asymptotic plateau, suggesting that other mechanisms may be involved in their low cataleptogenic liability. The present data confirm that 5-HT_1A receptor activation reduces or even completely prevents the cataleptogenic potential of novel antipsychotic agents. Further, they indicate that the balance of affinity and/or efficacy between D₂ and 5-HT_1A receptors profoundly influences their pharmacological activities, and will likely impact their therapeutic profiles.