Chronic administration of risperidone to healthy rats: a behavioural and morphological study.

Taking into account that most of the experimental research into the effects of antipsychotic drugs has mainly focused on behavioural aspects, the aim of the present work is to investigate the effects of a chronic therapeutic dose of risperidone (1 mg/kg/day during 140 days) on both behavioural and morphological aspects in healthy rats. The behavioural results revealed only minor modifications in prepulse inhibition, showing the risperidone-treated group higher values at 70 days of treatment with respect to the vehicle group. Moreover, in the open-field test, this group showed a greater incidence of grooming. In the active avoidance test, no differences were found between the groups studied. Additionally, in the morphological study performed to analyse cortical thickness and the number of GFAP-, CaBP-, PV- and Fos-immunostained cells no differences were seen between the two groups studied. It is important to note that the risperidone-treated group showed a slight increase in the total number of cells counted, although this increase was not significant. Our results indicate that the chronic administration of therapeutic doses of risperidone does not produce any dramatic behavioural or morphological changes in healthy animals.