The nature of copulation-induced

Estrous female cats (queens) were permitted 36-h periods of unrestricted mating activity; they then were injected with various doses of gonadotropin-releasing hormone (GnRH) at 36 h and allowed single copulations at 48 or 72 h of study. Serum luteinizing hormone (LH) levels were determined in samples collected prior to and 2 h after the initial copulation, before and 30 min after selected copulations during the next 10 h, and before and 30 min after copulations occurring at 20-24, 36, and 48-72 h, as well as 0, 15, and 30 min after the GnRH injections (0.3-3.0 micrograms/kg) at 36 h of study. Copulations occurred 14-20 times in 12 h and 20-36 times in 36 h. Copulation frequency (mean +/- SEM) decreased (p less than 0.05) from 5.5 +/- 0.6/2 h initially to 1.5 +/- 0.6/2 h during the subsequent 2-h period, and was 1.4 +/- 0.2/2 h at 12-36 h of study. Intromissions lasted 1-27 (8 +/- 0.3) s. Variation in durations of mounting by males (1.7 +/- 0.1 min; range, 0.3-10 min) or of the postcoital behavioral reactions displayed by the queens (2.5 +/- 0.1 min; range, 1-17 min) could not be related to animals or time of study. Peak serum LH levels (11-280 ng/ml; mean, 112 +/- 30 ng/ml) were observed at 2-4 h after the first mating. Mean LH steadily declined thereafter, reached basal values (less than or equal to 3 ng/ml) by 20-24 h, and remained low at 36 h.(ABSTRACT TRUNCATED AT 250 WORDS)