Premature Ovulation in the Domestic Fowl following Administration of Certain Barbiturates

Summary Ovulatory reactions of the first follicle of the hen's ovulation sequence to barbiturates, and to barbiturates with progesterone, are described. Ovulation was found to occur prematurely in a significant proportion of hens following the administration of some barbiturates (Dial, Ipral and Nembutal), rarely with barbital, and not at all with phenobarbital. Near subovulatory dosages of progesterone acted synergistically with two of the barbiturates (Dial and Nembutal) which themselves effect ovulation prematurely, an effect which was not found when progesterone was similarly administered with phenobarbital (preliminary observations). These several observations are consonant with the supposition that prematurity of ovulation following the administration of effective barbiturates results from neural excitation secondary to depression, excitation effecting over a humoral pathway the release of ovulation-inducing gonadotrophin from the anterior pituitary body.