Ovariectomy induces an increase, estrogen treatment after ovariectomy a decrease, in the level at which female rats regulate their body weights. Food-intake changes are transient, intake returning toward normal values as terminal body weight is approached; so these intake changes are probably secondary to effects on the weight-regulating system itself. Adrenalectomy blocks or reverses the weight gain which follows ovariectomy. This effect is not a matter of incapacity, but seems to reflect a resetting of the weightregulating system so that a low weight level is voluntarily maintained.

Progesterone injections (8 mg/kg/day or larger) resulted in decreased wheelrunning activity and an increased rate of body weight gain in seven female albino rats. These changes were evident from comparison to previous baseline determinations and to control animals. Injections of progesterone (40 mg/kg/day) into 11 ovariectomized animals had no effect on these measures. On the other hand, progesterone injections (16 mg/kg/day or larger) were effective in causing decreased activity and increased body weight when administered to seven ovariectomized rats receiving estradiol cyclopentylpropionate. These results indicate that progesterone can influence wheel running and body weight through a direct interaction with estrogen, possibly by interfering with the effects of estrogen on these measures.

In 2 experiments (N = 4S and 36) an effort was made to systematically manipulate amplitude of covert oral behavior. Ss silently read during: (a) silence, (b) auditory presentation of prose, (c) of backward prose, and (d) of white noise. Among the findings was that auditory presentation of prose and of backward prose during reading leads to a significantly greater amplitude of covert oral behavior than occurs during silence, but noise does not have this effect. It is concluded that the increased covert oral behavior is beneficial to S, perhaps by facilitating the reception and/or processing of language stimuli in the presence of auditory interference; or, alternatively, that Ss simultaneously respond to visual and auditory stimuli.

Estradiol and testosterone have differing influences on adrenal function. Estradiol augments adrenal corticosterone secretion by increasing ACTH secretion (1) and decreasing intraadrenal reduction of corticosterone through inhibition of adrenal 5a-reductase activity ( 2 ) . Estradiol also stimulates hepatic metabolism and clearance of corticosterone ( 3 ) . In contrast, testosterone inhibits ACTH secretion (4), but also facilitates adrenal corticosterone secretion through inhibition of adrenal 5a-reductase activity ( 2 ) . Hepatic metabolism of corticosterone is suppressed by testosterone ( 5 ) . These differences in pituitary, adrenal, and hepatic responses to testosterone and estrogen probably account for the sex differences in adrenal function seen in the rat (6).The effects of progesterone on adrenal function are not as well understood as those of the other gonadal hormones. Several authors have reported that progesterone decreases adrenal corticosterone secretion ( 7 ) and adrenal weight ( 7 , 8) when administered to female rats in doses exceeding 5 mg/day. Plasma corticosterone after ACTH treatment has been reported to be diminished after treatment with doses as low as 2 .O mg/day ( 9 ) . In contrast, Telegdy et al. have shown that progesterone administered at a dose of 1.5 or 1.0 mg/day increases adrenal corticosterone secretion ( 7, 10) and adrenal weight ( 7 ) . Ultrastructural changes in the fasciculata, reticularis, and glomerulosa of the adrenal cortex of female animals treated with progesterone ( 1 .O mg/ day) have been interpreted by Volk (1 1) to indicate hyperactivity of these structures. Givner and Rochefort ( 1 2 ) have recently reviewed and extended the data concerning the effects of synthetic progestogens on adrenal function in female rats. The most intensively studied of these, 6 alpha-methyl-pregn-4-en-3, 20 dione-1 7-acetate (medroxyprogesterone) , has usually been reported to produce adrenal atrophy, decreased plasma corticosterone concentration, and decreased in vitro corticosterone production. These effects have been ascribed in part to a block of pituitary ACTH secretion. Studies of the effect of progestogens on the adrenal function of ovariectomized animals are relatively few and contradictory.Edgren et al. (13) have reported that progesterone or 6-methyl-17 acetoxyprogesterone administration at a dose of 1 mg/day caused a decrease in adrenal weight of spayed females. In another experiment, only the latter preparation was effective. Brennen and Kray (14) found no significant effect of progesterone on adrenal weight when administered at either 1 .O or 3.0 mg/day to ovariectomized rats. The limited evidence concerning progesterone effects on male adrenal function indicates that injection of 10 mg/day results in decreased adrenal corticosterone secretion (9, 1 5 ) without a significant change in adrenal weight (15). In contrast, doses ranging from 0.3 rng to 3 mg/day caused increased adrenal weightThe experiments reported here were undertaken to determine if progesterone exerts an influ...

No abstract