The effects of indomethacin on plasma LH levels in female and male deermice (Peromyscus maniculatus).

The purpose of this investigation was to determine (1) the approximate time of the preovulatory LH rise in cyclic deermice, (2) the effect of indomethacin administration on plasma LH levels during the expected preovulatory LH rise, and (3) the effect of indomethacin administration on plasma LH levels in castrated male deermice. The data indicate that the preovulatory LH rise occurred at about 2200 h on proestrus and that indomethacin pretreatment significantly reduced plasma LH levels during that time. In addition, indomethacin significantly reduced plasma LH levels in castrated male deermice. We conclude that plasma LH levels remain low throughout the estrous cycle with the exception of the preovulatory "surge", that plasma LH levels in deermice are comparable to those reported for the rat, and that indomethacin pretreatment reduced plasma LH levels during periods when they were expected to be elevated (in castrated males and during the expected preovulatory LH rise in female deermice). The data are consistent with the hypothesis that the effect of indomethacin on plasma LH levels is due to an inhibitory effect on hypothalamic PG biosynthesis.