Effects of age and isolation on the evolution of catalepsy during chronic haloperidol treatment

ABSTRACT

Sixteen young (5 months) and 16 old (20-24 months) male Wistar rats, housed together or in individual cages were observed for cataleptic behavior 10, 20 and 30 days after the beginning of chronic haloperidol treatment (1.0 mg/kg, twice daily, for 30 days). Catalepsy was measured by the bar test. Age increased the duration of haloperidol-induced catalepsy of isolated and group-housed rats in the three observation sessions (old-isolated = 7.4 ñ 0.2; old-group housed = 7.5 ñ 0.1; young-isolated =6.3 ñ 0.2; young-group housed = 6.8 ñ 0.2 In seconds in session 1, for example). Conversely, isolation did not modify the sensitivity to the sensitivity to the cataleptic effect of haloperidol. Even more important, no differences in duration of haloperidol-induced catalepsy were observed among the three sessions for each group. The resultss indicate that under the experimental conditions employed the animals did not develop tolerance nor sensitization to haloperidol-induced catalepsy. In addition, neither age nor isolation modified the absence of effects of repeated haloperidol treatment on the catalepsy behavior of rats