150 



Richard M. Fraps 



the greater range in apparent duration of OIH release in the hypophysectomy 

 experiments can be attributed to difierences in techniques, birds, or in- 

 accuracies in estimating times of expected or actual ovulation. It seems 

 possible also, however, that an intact pituitary may be required beyond the 

 interim required for OIH release. 



Progesterone is known to disappear rapidly from the blood stream. 

 Taking this fact into account, Rothchild and Fraps (59) thought it improbable 

 that progesterone could act for 2 to 4 hr to assure the release of OIH in 

 adequate quantities. Progesterone, they suggested, may act promptly and 



Fig. 4. A parasagittal view of the hen's diencephalon and forebrain, showing the sites of 

 injections of progesterone made bilaterally at 1 mm. Solid circles, induced premature 

 ovulation; open circles, no premature ovulation; 1, posterior commissure; 2, anterior 

 commissure; 3, tractus septo-mesencephalicus; 4, optic chiasma; 5, oculomotor nerve; Pit, 

 pituitary; H, hyperstriatum; N, neostriatum; P, paleostriatum. From Ralph and Fraps (54). 



over a limited time in effecting the release of OIH, the intact pituitary being 

 essential for some time thereafter for secretion of a hormone required 

 for maintenance of the ovulable follicle. 



In further experiments, the ovulation-inducing effects of small quantities 

 of progesterone injected directly into various regions of the brain were 

 ascertained (54). Stereotaxic procedures used in placing lesions were followed 

 except for replacement of the electrode carrier by a microinjector with a 

 26 gauge needle. All injections into the brain were placed bilaterally, 5 /xg 

 progesterone in propylene glycol at each site in the definitive experiments. 

 Probably no more than half the quantity injected, or about 5 /ng/hen, 



