76 



Discussion 



animals were lesioncd at 18 to 20 days of age, examined daily for vaginal opening, 

 weighed 2 to 3 times a week and killed at 33 days of age. Littcrmates were used as 

 controls. 



In brief, the results obtained with a series of 23 hypothalamic lesions and 7 

 blank operated rats were similar to those discussed this morning by Dr. Harris: lesions 

 in the anterior hypothalamus were associated with precocious stimulation of the 

 reproductive system. 



Table 1 . Effects of Amygdaloid Lesions on Body and Organ 

 Weights and Vaginal Opening 



* Mean + standard error. 



t Probably significantly different from controls {P < 0.05). 



Figure 1 summarizes the antero-posterior locations of the nine lesions that were 

 judged effective on the basis of uterine weights that were significantly heavier (P < 0.01 ) 

 than those of 18 control rats. As illustrated, one lesion was large and involved most of 

 the structures in the anterior hypothalamus. The remaining lesions were more discrete 

 and, with the exception of one in the basal septum, involved parts of the medial 

 anterior hypothalamus. It should be noted that several of these lesions were effective 

 without sharing a common area of destruction. 



Of the 14 ineffective lesions in this series, bilaterally symmetrical destruction was 

 found in the thalamus, lateral hypothalamus, lateral preoptic region and olfactory 

 bulb. Four ineffective lesions were grossly asymmetrical. 



These data are in agreement with previously published work regarding the following 

 points: (1) lesions placed in the rostral hypothalamus induced precocious sexual 

 development, (2) no single hypothalamic structure could be implicated, (3) some 

 degree of anatomic specificity was suggested by the number and location of ineffective 

 lesions, and (4) the stress of cerebral trauma did not appear to be an adequate stimulus 

 for early ovarian stimulation. 



In contrast to the observations of Bogdanove and Schoen, the presence of corpora 

 lutea in ovaries of rats bearing effective hypothalamic lesions was not indicative of 

 damage to the arcuate nucleus : three of the four rats of this series that had corpora 

 lutea in their ovaries had lesions that spared the arcuate nucleus. Also, a small effective 

 lesion in this nucleus did not result in ovulation and luteinization. It appeared that 

 effective lesions, regardless of location, triggered prematurely an orderly sequence 

 of events which culminated in ovulation and corpora lutea formation, and autopsy at 

 day 33 might interrupt this sequence at any one of several stages. 



Having established some confidence in the specificity of this lesion response, we 

 next directed our attention to the amygdaloid complex. Table 1 summarizes some of 

 the results obtained. Twenty-four control rats had a mean uterine weight of 86.8 mg/ 

 100 gm body weight. Sixteen rats with lesions had uteri which were significantly 



