Preovulatory secretion of gonadotrophins and TSH in cyclic rats with small lesions in the preoptic area

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Abstract
Animals with unilateral or bilateral lesions, with 85 and 70% of intact preoptic area tissue remaining, respectively, returned to regular estrous cycles. By comparison with sham-operated controls, rats with lesions had more days with leukocytic smear in eahc of the 1st, 2nd or 3rd post-operative cycles, before returning to a 4-day cycle. Hormone measurements of blood collected during the afternoon of proestrus showed that, in rats with bilateral lesions, the duration of the preovulatory LH [luteinizing hormone] secretion was significantly shortened, although peak levels were unchanged. The initial phase of the preovulatory FSH [follicle stimulating hormone] secretion was lost. Much of the prolactin surge was also inhibited. The TSH [thyrotropin] surge was unaffected.