Effects of bromocriptine treatment on the expression of sexual behavior in male sheep (Ovis aries).
Twenty-three rams were treated twice daily with subcutaneous injections of bromocriptine or vehicle over 30 d during two seasons, spring and fall. Sexual behavior was observed and quantified to determine the effects of bromocriptine-induced hypoprolactinemia on mount attempt (MA), mount (M), and ejaculation (E) frequency of the rams upon exposure to estrous ewes. Behavioral responses and serum prolactin (PRL) concentrations were determined on a weekly basis before, during, and after the treatment period in each season. Treatment with bromocriptine caused a significant decrease in serum concentrations of PRL during both seasons (P < .01). Post-treatment period concentrations of PRL returned to pretreatment levels during the spring, whereas during the fall, post-treatment period PRL concentrations remained low (P < .05). The frequency of MA and M was lower during bromocriptine treatment relative to control rams in the spring (P < .05). The frequency of MA and M returned to pretreatment values after bromocriptine treatment was withdrawn. Ejaculation frequency tended to decrease during and after bromocriptine treatment relative to controls (P < .09). There was no effect of bromocriptine treatment on frequency of MA and M during the fall. During the fall, the frequency of E tended to decrease in bromocriptine-treated rams (P < .1). These data indicate that bromocriptine-induced hypoprolactinemia is associated with a significant diminution in expression of sexual behavior in rams. It is suggested that PRL modulates the intensity of expression of sexual behavior in rams, and this effect may be season-dependent.
Gloria
E
E
Department of Animal Sciences, Rutgers, State University of New Jersey, New Brunswick 08903.
Regisford
C
C
Katz
L S
LS
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology*; D004542:Ejaculation / Q000187:drug effects; D005260:Female; D008297:Male; D011388:Prolactin / Q000097:blood; D011897:Random Allocation; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D012756:Sheep / Q000502:physiology*
D001971:Bromocriptine; D011388:Prolactin