1202 



HORMONAL REGULATION 



was either wholly unmodified or, if modi- 

 fied, it was not in the direction of feminiza- 

 tion. Ball demonstrated that female hor- 

 mones, instead of feminizing the castrated 

 male rat as Kun (1934) had claimed, in- 

 creased their male activity. 



New evidence that hormones activate 

 adults in accordance with previously or- 

 ganized neural mechanisms rather than or- 

 ganizing new patterns has recently been 

 provided (Goy and Young, 1958). Female 

 guinea pigs from a genetically heteroge- 

 neous stock (T stock) displaying male-like 

 mounting spontaneously and from a strain 

 (strain 2) in which this behavior is not 

 shown (Goy and Young, 1957b) were 

 spayed and brought into heat with estrogen 

 and progesterone. On completion of the 

 control tests, 15-mg. pellets of testosterone 

 propionate were implanted into each ani- 

 mal. Estrus was again induced 24 days later 

 by repeating the previous treatment, and 4 

 months later, without additional androgen, 

 a final test was made. The average number 

 of mounts per test in the T stock animals 

 was 2.3, 41.8, and 3.8, respectively. In the 

 strain 2 animals the averages were 0.0, 0.0, 

 and 1.3. Two points are clear: (1) the an- 

 drogen activated the T stock females to 

 display mounting at the time of the second 

 test, but there was no lasting, organizational 

 effect; (2) the androgen was not effective in 

 stimulating mounting in a strain which does 

 not display this behavior spontaneously, 

 consequently in these animals there was 

 no evidence either for an activating or an 

 organizing action. 



C. AGE OF THE ANIMAL AND THE HORMONAL 

 REGULATION OF MATING BEHAVIOR 



Most of the attention devoted to the hor- 

 monal regulation of mating behavior has 

 been centered on the adult during the period 

 of reproductive activity. No investigator 

 has tested a group of animals from youth to 

 old age in an effort to relate any changes 

 in the strength and pattern of behavior to 

 changes in quantity of hormone or in reac- 

 tivity of the tissues mediating such be- 

 havior. Considerable information exists but 

 it is fragmentary and interpretation is diffi- 

 cult. 



Injections of a pituitary gonadotrophic 



substance (hebin) into 3-day old male 

 chicks were followed 6 days later by crow- 

 ing and after 10 days by initial treading 

 reactions (Domm and Van Dyke, 1932a). 

 Injections of androgen were followed by 

 crowing on the 4th day of age and by tread- 

 ing on the 15th day (Hamilton, 1938; Brene- 

 man, 1939; Noble and Zitrin, 1942). A com- 

 parison of the effective quantities in young 

 birds and in somewhat older cockerels 

 (Davis and Domm, 1943) can only be made 

 by inference; 0.5 to 1.0 mg. daily seems to 

 have been sufficient for the younger birds, 

 whereas 2.50 to 3.75 mg. were required for 

 two older birds. Apparently the sensitivity 

 of 30-day chicks was not greater than that 

 of 2-day chicks. 



Of the investigations in which manunals 

 were used, that by Steinach and Kun (1928) 

 was one of the first. Control male rats in 

 their colony were not attaining maturity 

 until 60 to 70 days of age, but experimental 

 animals given 9 to 18 injections of a water- 

 soluble extract of anterior pituitary begin- 

 ning at 4 to 5 weeks of age displayed mature 

 sexual behavior as early as 38 to 45 days of 

 age. More recently, data have been obtained 

 bearing on the response of prepubertal rats 

 and guinea pigs to testosterone propionate. 

 The report by Stone (1940) that the median 

 age of the first copulation (mounting, pal- 

 pation and pelvic thrusts with intromission ) 

 in the intact rat was set ahead about 20 

 days was confirmed by Beach (1942c). In 

 Stone's experiment 0.62 mg. testosterone 

 propionate was injected daily; in Beach's 

 experiment 1.0 mg. was given. As in the 

 case of the chicken, comparison with the 

 adult is hazardous, but the report (Beach 

 and Holz-Tucker, 1949) that 50 to 75 /.g. 

 testosterone daily is necessary for the main- 

 tenance of the preoperative level of copula- 

 tion in adults suggests that the sensitivity 

 of the young rats used by Stone and Beach 

 to testosterone propionate was less than 

 in the adults used by Bcacli and Holz- 

 Tucker. 



Results from two studies of young guinea 

 pigs are presented for comparison with 

 those obtained from the chicken and rat. 

 The development of mating behavior was 

 followed by weekly tests from within a 

 week after birth to. 120 days of age (Riss, 



