Delaying Action of Gonadotropins on Ovulation in the Hen.

Abstract

Antiadrenergic, anticholinergic or central depressant drugs suppress or delay, in varying proportions, ovulation of the 2d or C2 follicle of the hen''s sequence following their administration 18-20 hours before normally expected ovulation. To counteract these effects, a whole anterior pituitary (AP) preparation from cocks was injected intramuscularly shortly before injection of several of the drugs. Incidence of suppressed ovulations was increased by AP preparation, and increased proportions of suppressed ovulations exhibited C1 lapses. Intramuscularly injected 18-19 hours before expected C2 ovulation, the AP preparation alone suppressed ovulation in most hens, with a high proportion of C1 lapses. Under similar conditions, luteinizing hormone (LH) or follicle stimulating hormone (FSH) from cock pituitaries suppressed ovulation in some hens. Administration of 0.02 mg LH + 2 mg FSH/hen suppressed ovulation in 93% of injected birds, and all of these exhibited the C1 lapse. Progesterone injected at about the hour of normally expected release of ovulation-inducing hormone (OIH) effected ovulation in most hens previously treated with the AP preparation, indicating that gonadotropin-induced lapses resulted from a transient "blockade" of the nervous mechanism controlling OIH release.