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THE PREOPTIC REGION OF THE BRAIN AND 

 ITS RELATION TO OVULATION* 



John W. Everett 



Nearly thirty years ago Hohlweg and Junkmann (23) postulated the 

 existence of a sex center in the hypothalamus. Today there is no doubt that 

 many of the sexual, as well as non-sexual, functions of the adenohypophysis 

 are under control of the central nervous system through the mediation of 

 the hypothalamus and the special neurovascular linkage afforded by the 

 hypophysial portal veins. Theory has moved on and now one postulates 

 multiple mechanisms separately controlling diverse aspects of adenohypophy- 

 sial function. One may question whether anatomically discrete "centers" exist; 

 there is good reason to think that elements of several mechanisms may be 

 anatomically interwoven and that each may involve an interplay among 

 several parts of the brain. 



We are concerned here with only one of these mechanisms and with only 

 one basic method of experimental study, electrical stimulation of the brain. 

 No attempt will be made to review in detail the historical background for 

 the induction of ovulation by this means. It is only necessary to call to mind 

 a series of studies by naming the investigators : Marshall and Verney (28) ; 

 Haterius and Derbyshire (21); Harris (19,20); Markee, Sawyer and 

 Hollinshead (27); Kurotzu, Kurachi and Ban (26). Whereas these several 

 investigations were carried out in the rabbit, a species that ovulates "reflexly", 

 more recent studies have shown that ovulation can be induced by similar 

 means in the rat, an animal that normally ovulates spontaneously. The first 

 published record is the abstract of a paper by Critchlow (6), noting that 

 proestrous cycling rats, in which the spontaneous ovulation was prevented by 

 the administration of pentobarbital, could be induced to ovulate by electrical 

 stimulation of the hypothalamus with electrodes resting close above the 

 median eminence. This work was reported in full in 1958 (7). Meanwhile, 

 Bunn and Everett (4) had been successful in inducing ovulation by stimula- 

 tion of the amygdaloid complex in rats that had been made constant-estrous 

 by continuous illumination. 



The experiments that will be reported here are directly based on Critchlow's 

 work, which in turn was based on the work of Everett and Sawyer (13). These 



* These investigations were partially supported by grants from the National Science 

 Foundation (G4431 and G9841). 



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