1350 



HORMONAL REGULATION OF BEHAVIOR 



the brain of goats would cause them to 

 drink. Miller, Richter, Bailey and South- 

 wick (Miller, 1957b) repeated this observa- 

 tion in cats, and found that the injection of 

 no more than 0.15 cc. of slightly hypertonic 

 (2 per cent) NaCl solution caused an in- 

 crease in the volume of water drunk by the 

 animals, whereas injection of the same 

 amount of distilled water decreased con- 

 sumption. Cross and Green (1959) observed 

 the activity of single neurones in the hypo- 

 thalamus of rabbits, and found that the rate 

 of firing of neurones in the supra-optic nu- 

 clei was increased by small injections of 

 hypertonic NaCl into the carotid arteries, 

 whereas the rate of firing of neurones in the 

 paraventricular nuclei was reduced. These 

 authors were primarily interested in the 

 effects of blood tonicity on posterior pi- 

 tuitary secretion, but their results, taken 

 in conjunction with those of Andersson and 

 of Miller, further indicate the existence of 

 local effects on hypothalamic activity, ex- 

 erted by humoral conditions known to be 

 relevant to the elicitation of various be- 

 havior patterns. 



With the exception of the brief report by 

 Fisher (1956), none of the material on di- 

 rect central behavioral effects of hormones 

 has been related directly to the elicitation of 

 parental behavior. However, the general 

 background of evidence clearly indicates 

 that central influences of the relevant hor- 

 mones will be an important factor in future 

 research on this, as on other types of be- 

 havior. 



The problem of the specificity of central 

 neuro-endocrine mechanisms. Some of the 

 evidence cited above has been noted by 

 Morgan (1959) as supporting the concept 

 of "centers" for motivation and for be- 

 havior, as places in which "drive" or motiva- 

 tion is aroused, and also from which be- 

 havior is "emitted" (Stellar, 1954). As 

 Hinde (1959) points out, the evidence at 

 hand does not permit the firm conclusion 

 that all the important aspects of either 

 the motivation or the organization of the 

 types of behavior patterns we are discussing 

 are gathered together into single loci. 



Copulation, or artificial stimulation of 

 the vagina, are followed by changes in 

 electrical activity which can be detected 



by electroencephalographic techniques, in 

 both the female domestic cat (Porter, Cava- 

 naugh, Critchlow and Sawyer, 1957) and 

 rabbit (Sawyer and Kawakami, 1959). 

 These aftercoital effects can be induced by 

 treatment with some pituitary hormones, 

 such as gonadotrophins and posterior pi- 

 tuitary hormones, which are known to be 

 released as a result of stimuli associated 

 with copulation (Kawakami and Sawyer, 

 1959a). Sawyer (1959) and his co-workers 

 therefore conclude that these changes in 

 central nervous activity are induced by the 

 effects of the hormones on the nervous sys- 

 tem, in effect a feed-back system. Kawakami 

 and Sawyer (1959b) found that various hor- 

 mones affect the threshold for the arousal of 

 these electroencephalographic changes by 

 electrical stimulation of the brain. 



Now, Sawyer (1959) points out that the 

 effects of ovarian hormones on the thresh- 

 olds for brain stimulation are very wide- 

 spread and generalized. Effects of hormones 

 on the brain-stem reticular formation (Dell, 

 1958a, b; Sawyer, 1958) or in other parts 

 of the brain may result in quite specific 

 changes in the activity of, say, a hypo- 

 thalamic nucleus, although the effects of the 

 injected or endogenous hormone might not 

 themselves be specific to that "center." 



The work on the injection of minute 

 quantities of hormones into specific loci, 

 such as that of Harris, Michael, and 

 Scott (1958), and Flerko and Szentogothai 

 (1957), does not yet demonstrate that spe- 

 cific "centers" are selectively sensitive to 

 the particular hormones which normally 

 arouse behavior mediated by those centers. 

 The fact that ovarian fragments cause 

 suppression of pituitary activity when im- 

 planted into one hypothalamic area, and 

 not in another, may mean either that the 

 two areas are differentially sensitive to 

 estrogen, or that the nuclei of that region of 

 the brain are all sensitive to estrogen, but 

 only some of them are so related to the 

 pituitary gland that their activity can cause J 



changes in pituitary secretion. Similarly, * 



the demonstration that small amounts of 

 estrogen released into certain hypothalamic 

 nuclei induce female sex behavior should 

 undoubtedly be followed by attempts to de- 

 termine whether other kinds of chemical 



