Coitus-induced release of luteinizing hormone in the proestrous rat: fantasy or fact?

The influences of mating on serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels were evaluated in 4-day cyclic proestrous rats of the Wistar strain. Blood samples were collected via guillotine from mated and unmated controls at 1900-2000 h or 2100--2200 h. Serum LH levels were determined by two independent radioimmunoassays. There were no significant differences in LH measurement between assays. At 1900--2000 h, LH levels were high, but not significantly different, in both the mated and unmated control animals. By 2100-2200 h, serum LH concentration had dropped in unmated controls but was significantly elevated in mated animals. There was no significant elevation in FSH either 1900-2000 h or 2100--2200 h on the evening of proestrus. The data indicate that when LH levels are normally high, coitus cannot further potentiate LH release. However, when LH levels are declining, coitus is an effective and adequate stimulus to initiate elevations in serum LH.