HIGH AND LOW REACTIVITY TO NOVELTY AND SEXUAL-BEHAVIOR IN MALE RATS

A rat's level of activity when exposed to a novel environment has been shown to be associated with enhanced sensitivity to the locomotor-act ivating and rewarding effects of dopamine-releasing substances. Male r ats were divided into high responders (HRs) and low responders (LRs), depending on their activity in a 90-min test in an unknown environment . Tests for sexual behavior were then performed. It was found that the HRs had longer intromission and ejaculation latencies as well as redu ced intromission ratios and number of ejaculations at the first test. The number of mounts made by the HRs, however, was higher than that ma de by the LRs. In the second and third tests, there was no difference between groups. Other groups of HRs and LRs were treated with amphetam ine, 1 mg/kg, before the sexual behavior test as well as before a seco nd test of ambulatory activity. The locomotor response to amphetamine was greater for HRs than for LRs. However, with regard to sexual behav ior, HRs differed from LRs in a way similar to that observed in untrea ted animals. These data show that there is no relationship between rea ction to novelty and sexual motivation, and that the effects of amphet amine on sexual behavior are similar in HRs and LRs.