1348 



HORMONAL REGULATION OF BEHAVIOR 



They suggest that the hormone acts, not 

 by activating or sensitizing a motor struc- 

 ture in the central nervous system, but by 

 changing the pattern of afferent controL 

 Changes in olfactory acuity and in the 

 nasal mucosa characterize different stages 

 of the human menstrual cycle (Elsberg, 

 Brewer and Levy, 1935; Henderson, 1956), 

 and olfactory acuity is affected by sex hor- 

 mone administration to hypogonadal women 

 (Schneider, Costiloe, Howard and Wolf, 

 1958; for review see Le Magnen, 1953). 



As Morgan (1959) has pointed out, it is 

 not at all necessary that a hormonal effect 

 on behavior be through either exclusively 

 peripheral or exclusively central influences. 

 Both types of effect of the same hormone 

 may contribute. We earlier presented evi- 

 dence that the condition of mammary en- 

 gorgement makes some contribution to the 

 regulation of maternal nursing behavior. 

 When Seward and Seward (1940) tested 

 I'ictating guinea pigs in a device in whicli 

 they had to cross a l)arrier to get to their 

 young, and used the stiength of the tendency 

 to cross the barrier as an estimate of the 

 intensity of motivation to nurse, they found 

 that animals tested just after being milked 

 consistently showed less of this "drive"" than 

 those tested when their mammary glands 

 were full of milk. However, abdominal 

 sympathectomy, which renders the mam- 

 mary glands incapable of res])onding to hor- 

 mone stimulation (Bacq, 1932a, 1); Coujard, 

 1943; Champy, Coujard and Demay, 1950), 

 often fails to prevent the appearance of ma- 

 ternal attempts to nurse the young, al- 

 though, in most of these reports, it is not 

 clear whether diffei'ences between animals 

 with and without previous nursing experi- 

 ence may be important. It is nevertheless 

 clear that, although the state of mammary 

 engorgement, induced by hormones, prol)a- 

 bly contributes to the regulation of ma- 

 ternal nursing behavior, other factors, 

 possibly including central effects, are also 

 present. 



3. Central Hormonal Effects on Behavior 



In recent years, a good deal of evidence 

 has been accumulating to show that many 

 of the effects of hormones on behavior pat- 

 terns are by wav of direct chemical effects 



of the hormones on the central nervous 

 system. 



The development oj neural mechanisms. 

 Kollros (1942, 1943) found that the im- 

 plantation of small pellets of thyroxine- 

 saturated agar into the brain of the frog 

 tadpole could cause the lid-closure reflex, 

 the appearance of which is associated with 

 metamorphosis, to develop earlier on the 

 side of the animal on which the pellet was 

 im{)l anted than on the other side, where a 

 control pellet without thyroxine was im- 

 planted. Kaltenbach (1953a, b) showed that 

 a variety of structures could be made to 

 metamorphose earlier than normal by local 

 application of thyroxine. Weiss and Ros- 

 setti (1951 ) found that local application of 

 thyroxine in immature tadpoles caused the 

 premature atrophy of Mauthner's cells, ac- 

 companied by accelerated growth of neigh- 

 boring nerve cells, both phenomena associ- 

 ated with normal metamorphosis. 



Additional evidence that humoral influ- 

 ences associated with the actions of hor- 

 mones play a role in the differentiation of 

 neural structures mediating various be- 

 liavior patterns may be found in a recent 

 important study by Phoenix, Goy, Gerall 

 and Young (1959). These workers adminis- 

 tered testosterone propionate to mother 

 guinea pigs during pregnancy, and then 

 studied the sexual behavior of their off- 

 spring after they reached adulthood. No 

 effects were observed on male offspring. 

 Genetically female offspring showed greatly 

 reduced capacity for female sexual be- 

 liavior, and increased tendencies to per- 

 form male sexual behavior. The androgen 

 treatment similarly resulted in morpho- 

 logic hermaphrodites, genetic females in 

 which the external genitalia were, at birth, 

 not distinguishable from those of untreated 

 males. Since the amount of male hormone 

 re(iuired to cause suppression of female 

 sexual behavior was less than that required 

 to cause morphologic abnormalities, it is 

 not likely that the effects on sex behavior 

 were mediated by changes in the sex organs. 

 Various abnormalities of the ovarian cycle 

 were also noted (Tedford and Young, 1960), 

 which together with the disturbances of 

 sexual behavior suggest that the effect of 

 the androgen treatment was, or included. 



