84 Charles H. Sawyer and M. Kawakami 



This afterreaction to coitus, whose EEG characteristics were observed 

 simultaneously with the behavioral changes, seems to occur ordinarily in 

 the undisturbed female rabbit. It does not develop in a noisy room and it was 

 missed in earlier observations probably because its behavioral characteristics, 

 in the absence of a simultaneous recording of the unusual EEG pattern, are 

 not dramatic. It cannot be induced in the anestrous rabbit by vaginal stimu- 

 lation but it is readily evoked by this method in the estrous, estrogen-treated 

 female. It does not occur in the male rabbit as a sequel to copulation. 



At first it was thought that the EEG afterreaction did in fact represent 

 correlates of nervous activation of the hypophysis. However, it soon became 

 apparent that the time course was too late for such a relationship. An anti- 

 nervous blocking agent must be injected within a minute post coitum to 

 prevent ovulation (33) whereas the period of "EEG hyperarousal" or 

 hippocampal hyperactivity may not appear for half an hour or more post 

 coitum. By this time presumably considerable ovulating hormone has already 

 been released, for enough has reached the circulation within an hour to make 

 the further presence of the pituitary gland unnecessary for ovulation (34-36). 

 So if the EEG afterreaction is more than coincidentally linked to the release 

 of ovulating hormone it is more likely related to the discharge process itself 

 or perhaps to the action of the released hormone on the brain as a direct 

 feed-back mechanism. The reaction occurs in ovariectomized rabbits so the 

 principal target organ of ovulating hormone is not involved in the feed-back 

 mechanism (32). 



This feed-back hypothesis led to attempts to induce a spontaneous EEG 

 afterreaction, in the absence of coitus or vaginal stimulation, with the use 

 of exogenous pituitary hormones and placental gonadotropins (37). The 

 attempts were successful with purified preparations of pituitary luteinizing 

 hormone (LH) (Fig. 5, A-D), human chorionic gonadotropin (HCG), equine 

 gonadotropin (PMS) and also with lactogenic hormone (LTH) and the 

 neurohypophysial principles, oxytocin and vasopressin. The other adeno- 

 hypophysial tropins, follicle stimulating hormone (FSH) (Fig. 5, A^-D^), 

 thyrotropin (TSH), adrenocorticotropin (ACTH) and growth hormone 

 (somatotropin), all gave negative results. Interestingly all of the pituitary 

 principles whose injection resulted in an EEG afterreaction are released in 

 response to coitus. The results are consistent with the hypothesis that the 

 post-coital EEG afterreaction is functionally related to the feed-back of 

 these released pituitary hormones. Teleologically such a system would serve 

 a useful purpose in shutting off the hypothalamo-hypophysial mechanism 

 for activation of release of ovulating hormone. 



The essential nature of the EEG afterreaction is incompletely understood. 

 It has certain characteristics of a psychomotor seizure, and it appears to be 

 related to the condition of adynamia described by Hess (38) and the "arrest 

 reaction" of Hunter and Jasper (39). The latter is likened to a petit mal attack. 



