Effects of hypothalamic and preoptic lesions on reproductive behavior in male rats
Christensen, L.W.; Nance, D.M.; Gorski, R.A.
Brain Research Bulletin 2(2): 137-141
1977
ISSN/ISBN: 0361-9230 PMID: 880486 DOI: 10.1016/0361-9230(77)90010-7Document Number: 435231
Adult male rats, which were selected on the basis of showing complete patterns of male copulatory behavior on 2 prior tests, were castrated 6 wk prior to brain surgery. Animals were divided into 3 groups and given small bilateral lesions in the dorsomedial preoptic area (POA), ventromedial hypothalamus (VMH), or sham operations. Starting 10 days postsurgery, all animals were injected with estrogen alone and estrogen plus progesterone, and tested twice for lordosis behavior. Ten days following the female behavior tests, animals were injected daily with testosterone propionate for 13 days and tested for masculine sexual behavior on injection days 5, 9 and 13. Low levels of lordotic behavior were observed for POA and VMH animals on both tests for female sex behavior and were comparable to sham operated animals. In terms of all dependent measures of male copulatory behavior, animals with VMH lesions showed significantly higher levels of male sex behavior with shorter latencies than sham animals across all 3 behavior tests. POA lesioned rats showed little or no male sex behavior on any test and were significantly inferior to sham operated animals. The POA and VMH appear to exert excitatory and inhibitory control, respectively, over male copulatory behavior in male rats.
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