A central 5-HT2 receptor mechanism plays a key role in the proestrous surge of luteinizing hormone in the rat.

The role of serotonin (5-HT) in generating the spontaneous preovulatory surge of luteinizing hormone (LH) has been investigated by studying the effect of ketanserin (a mixed 5-HT2/alpha 1 adrenoreceptor antagonist); the selective 5-HT2 receptor antagonist, ritanserin; and the selective alpha 1 adrenoreceptor antagonist, prazosin, on the plasma concentrations of LH during the afternoon of proestrus in conscious Wistar rats. Sequential blood samples for hormone estimation were taken through intra-atrial cannulae previously implanted under halothane anesthesia. All three drugs blocked the LH surge; ketanserin, but not ritanserin or prazosin, also blocked basal LH release. These results provide the first robust evidence for the fact that a 5-HT2 receptor as well as an alpha 1 adrenoreceptor mechanism is involved in the LH surge generator.