KETANSERIN EFFECTS ON RAT BEHAVIORAL-RESPONSES - MODIFICATIONS BY THEESTROUS-CYCLE, OVARIECTOMY AND ESTRADIOL REPLACEMENT

The present investigation was designed to explore the influence of est rous cycle phase, ovariectomy, and estradiol replacement on the behavi oral effects of the 5-HT2 receptor antagonist, ketanserin. The paramet ers under investigation were ketanserin-influenced acquisition of cond itioning avoidance responses (CARs), and the performance of some spont aneous motor behaviors. Ketanserin (KET 3 mg/kg) injected subcutaneous ly 30 min before testing improved active conditioned avoidance in inta ct female rats at estrus, and in ovariectomized (OVX) rats with estrad iol replacement. Furthermore, KET impaired performance in female rats at diestrus and after ovariectomy. In male rats, which were included i n this study in order to compare their behavioral responses with those exhibited by female rats, KET administration enhanced acquisition of CARs. These results provide behavioral evidence for the hypothesis tha t central serotonergic activity is a function of the hormonal status o f the animal. An additional segment of the present study focussed on m otoric behaviors. Spontaneous motor activity, number of rears, and tim e spent in grooming behavior were significantly increased by KET in al l groups studied. In contrast, blockade of 5-HT2 receptors failed to i nduce significant changes in the number of head shakes. Relationships between ovarian hormones and the central serotonergic system are discu ssed. (C) 1997 Elsevier Science Inc.