80 



Charlks H. Sawyer and M. Kawakami 



That sex steroids do, directly or indirectly, innucncc the central nervous 

 system is evidenced also by their obvious effects on reproductive behavior 

 (9, 10). A direct action is implied by the results of experiments of Kent and 

 Libcrman (11), Fisher (12) and Harris, Michael and Scott (13) in which they 

 injected steroids directly into the brain. Whether the hypothalamic area 

 controlling gonadotropic function is identical to the area controlling repro- 

 ductive behavior and whether either is a primary focus of steroid action are 

 questions to be considered in the present paper. 



In this report the authors attempt to summarize their recent experiments 

 on the effects of pituitary and gonadal hormones on thresholds of central 

 nervous activity as assessed by electroencephalographic (EEG) recording 

 methods. These effects are correlated with changes in estrous behavior and 

 thresholds of pituitary activation in the rabbit. Earlier results obtained with 

 electrical stimulation and lesioning techniques are presented as an introduc- 

 tion to the anatomy of the hypothalamus, rhinencephalon and brainstem. 



STIMULATION-LESION EXPERIMENTS; 

 THE ANATOMICAL SUBSTRATE 



Activation of the release of pituitary ovulating hormone in the rabbit by 

 localized electrical stimulation of the hypothalamus and preoptic area, 

 respectively, was achieved in 1937 independently by Harris (14) and Haterius 



OPTIC 

 CHIASM 



NFUNDIBULAR 

 PROCESS 



Fig. L Location of gonadotropic and sex behavioral areas in the hypothalamus of the 



female rabbit and the female cat. C&R TROPIC, common area controlling release of 



pituitary ovulating hormone in the cat and rabbit. CB and RB, areas in which lesions 



induce permanent anestrus in the cat and rabbit respectively. 



