131() 



HORMONAL REGULATION OF BEHAVIOR 



Allan and Wiles ( 1932) must be mentioned 

 at this point. They found that cats hypo- 

 physectomized during pregnancy deserted 

 their kittens immediately after parturition. 

 Since hypophysectomized rats retrieve ap- 

 parently normally, even when the hypophy- 

 sectomy was accomplished during preg- 

 nancy (Obias, 1957), the different results 

 obtained by Allan and Wiles presumably 

 represent a difference between cats and rats 

 with respect to the method of control of the 

 mother's behavior toward the young. 



Erhardt (1929) induced a nonpregnant 

 female rhesus monkey to adoi)t a neonatal 

 guinea pig by injecting her with an anterior 

 l^ituitary extract. Since that time, consider- 

 able additional evidence has accumulated 

 implicating hypophyseal hormones in the 

 regulation of retrieving behavior. Riddle, 

 Lahr and Bates (1942) found that prolactin 

 caused substantial increases in retrieving 

 behavior in both male and female rats, 

 whether intact or gonadectomized (Riddle, 

 Lahr and Bates, 1935a, b; Riddle, Hollan- 

 der, Miller, Lahr, Smith and Marvin, 1942). 

 Luteinizing hormone was similarly able to 

 increase retrieving behavior. The fact that 

 the luteinizing hormone increased retriev- 

 ing even in gonadectomized animals sug- 

 gests that there was present in this prep- 

 aration some material capable of acting 

 directly on nongonadal parts of the soma, 

 and Riddle and Bates (1939) note that Rid- 

 dle's luteinizing hormone preparations con- 

 tained "some" prolactin. Prolactin, of 

 course, exerts a luteotrophic action on the 

 ovary (Meites and Shelesnyak, 1957), but 

 since it is effective in inducing retrieving 

 behavior in gonadectomized animals, its 

 luteotrophic effect cannot be the only source 

 of its action in this situation. 



FSH seems to have no effect on retrie\-- 

 ing behavior (Riddle, Lahr and Bates, 

 1935a). Animals injected with this sub- 

 stance retrieved young in about the same 

 percentage of cases as did untreated ani- 

 mals (Riddle, Lahr and Bates, 1935b). 



ih) r/iyro/f/. McQueen-Williams (1935a, 

 b ) found that removal of the thyroid glands 

 in male rats induced retrieving and other 

 aspects of parental care of the young, a 

 finding confirmed by Riddle, Lahr and 

 Bates (1936). Thyroidectomy increased the 

 incidence of retrieving in tests of male rats 



from about 21 per cent to about 45 per cent 

 (Riddle, Lahr and Bates, 1942). 



Dispensa and Hornbeck (1941) injected 

 desiccated thyroid into rats during preg- 

 nancy and found no effect on retrieving or 

 other aspects of maternal care. Chu (1945) 

 found that rabbits that became pregnant 

 after thyroidectomy Jailed to care for the 

 young. It should be noted, however, that 

 the behavior of the rabbit differs from that 

 of the rat in that retrieving does not nor- 

 mally occur in this species (Ross, Denen- 

 l)erg, Frommer and Sawin, 1959). 



(c) Gonads. Castrated male mice show 

 retrieving behavior after some association 

 with the young (Leblond, 1940), but no 

 data are available to indicate whether this 

 behavior is more frecjuent or more intense 

 than that normally shown by intact males 

 in the same laboratory. Riddle, Lahr and 

 Bates (1942) noted that castration does not 

 itself appreciably increase retrieving be- 

 havior in either male or female rats. How- 

 ever, almost all of the substances which, in 

 their study, were found to increase retriev- 

 ing behavior ie.g., prolactin, "luteinizing 

 iiormone" etc.) were more effective in gon- 

 adectomized (whether male or female) than 

 in intact animals. 



Testosterone injections cause some in- 

 crease in retrieving behavior in castrated 

 males, intact females, and ovariectomized 

 females, but not in intact males (Riddle, 

 Lahr and Bates, 1942). Fisher's (1956) lo- 

 cal injections of sodium testosterone sulfate 

 into the hypothalamus induced retrieving 

 behavior in some cases. As I noted in con- 

 nection with the induction of nest-building 

 in Fisher's experiment, no data yet exist for 

 comparison of the effects of this androgen 

 with those of other hormones applied in 

 the same manner. 



Riddle, Lahr and Bates (1936) found that 

 progesterone was as effective in increasing 

 retrieving behavior as was prolactin. 



Retrieving behavior seems to be sup- 

 jiressed by the administration of estrogenic 

 substances. Riddle, Lahr and Bates (1942) 

 treated virgin female rats with estrone for 

 20 to 26 days. Under this treatment, the 

 mammary glands developed to a degree 

 similar to that found late in pregnancy, but 

 none of the experimental animals would re- 

 trieve 3-day-old young rats during the pe- 



