Boris B. Gorzalka

Neonatal androgenization and the development of estrogen responsivity in male and female rats

Abstract Male and female rats castrated in adulthood, male rats castrated on the day of birth, and female rats administered 250 μg of testosterone propionate on the day of birth were administered various doses of estradiol benzoate in adulthood and tested for the display of lordosis. The females and neonatally castrated males exhibited a dose-dependent response to estrogen. The control males and neonatally androgenized females showed few lordosis responses when mounted by nonexperimental males regardless of the dose of estrogen administered. The combination of progesterone with the estrogen treatment did not facilitate lordosis responding in the males and neonatally androgenized females, nor did an extensive adaptation period to the test arena, nor did 10 days of treatment with 200 μg estradiol benzoate daily. It was concluded that males and neonatally androgenized females are less responsive to estrogen in adulthood than are females and neonatally castrated males.

The effects of progestins, mineralocorticoids, glucocorticoids, and steroid solubility on the induction of sexual receptivity in rats☆

Abstract In the first experiment, progesterone and its 5α-reduced metabolite, 5α-dihydroprogesterone, dissolved in two different vehicles were compared for their effectiveness in facilitating lordosis behavior in ovariectomized estrogen-primed rats. When dissolved in oil vehicle, 5α-dihydroprogesterone was less effective than progesterone. However, when dissolved in Tween 80 solution, the two progestins were equally effective. In the second experiment, adrenal corticoids dissolved in Tween 80 solution were tested for their relative ability to facilitate sexual receptivity. Progesterone, desoxycorticosterone, and desoxycorticosterone acetate were equally effective in facilitating sexual receptivity. Aldosterone, corticosterone, and corticosterone acetate were no more effective than the vehicle in facilitating sexual receptivity.

The effects of progesterone and its metabolites on the induction of sexual receptivity in rats

Estrogen-primed female rats were administered progesterone, 5 a-pregnan-3,20-dione, 5a-pregnan-3a-ol-20-one, 5a-pregnan-3β-ol-20-one, 4-pregnen-20a-ol-3-one, and 5a-pregnan-20a-ol-3-one in oil or oil alone and tested for the display of lordosis behavior 3 and 5 hr after progestin treatment. Progesterone was the most effective progestin in facilitating lordosis behavior. 5a-Pregnan- 3,20-dione and 5a-pregnan-3a-ol-20-one were partially effective, while the other progestins were no more effective than oil. The data suggest that the neuronal system which controls lordosis behavior is not entirely specific for progesterone.

Effects of an estrogen antagonist on behavior and on estrogen retention in neural and peripheral target tissues

Abstract Sexual receptivity was induced in ovariectomized female rats by a single intravenous injection of 4μg or more of estradiol-17β. Intravenous administration of the estrogen antagonist CI-628 up to 6 hr after the estrogen injection completely inhibited subsequent lordotic responses. A partial inhibition of behavior was observed when the antiestrogen was given 8 or more hr after the estrogen. Parallel analysis of retention of radioactivity following 3 H-estradiol administration in neural and peripheral tissues revealed that CI-628 displaced the hormone from uterine and hypothyseal receptor sites. However, radioactivity was not displaced from the anterior and posterior hypothalamus, anterior mesencephalon and cerebral cortex. The results suggest that the inhibitory action of CI-628 on behavioral receptivity was not mediated by displacement of estradiol from neural sites. Thus the model relating estradiol displacement to estrogen antagonism in peripheral tissues was not supported for neural tissues.

Studies on the effects of intracerebral actinomycin D implants on estrogen-induced receptivity in rats☆

Abstract Ovariectomized female rats were injected with estrogen and progesterone and actinomycin D was implanted into different brain areas. Implants of actinomycin D inhibited estrogen-induced lordosis behavior when applied to the preoptic region within 12 hr of estrogen treatment regardless of whether the interval between implantation and testing was 29, 38, or 68 hr. Implants 21 hr after estrogen treatment were ineffective. Attempts to localize the site of action showed that implants into the preoptic region were effective even when the implant cannulae did not pierce the ventricles, that implants into the caudate nucleus were ineffective even if the cannulae pierced the lateral ventricles, and that implants into the third ventricle were highly effective in inhibiting lordosis behavior.

Genetic regulation of hormone action: Selective effects of progesterone and dihydroprogesterone (5α- pregnane — 3,20 — dione) on sexual receptivity in mice

Abstract Lordosis behavior was measured in estrogen-primed, castrated female mice of the CD-1 and Swiss-Webster strains. In CD-1 mice, repeated stimulation with progesterone or dihydro-progesterone for at least 5 weeks was required for maximal facilitation of the lordosis response. The data further indicated that progesterone and dihydroprogesterone were acting via independent systems. In Swiss-Webster mice, progesterone, but not dihydroprogesterone, was similarly capable of inducing a high probability of lordosis responses.

Inhibition not facilitation of sexual behavior by PCPA.

It has been proposed that estrous behavior in the female rat may be under tonic inhibition by a central serotonergi system. Studies conbining estrogen priming and the pharmacological depletion of serotonin have provided some support for this hypothesis. Some evidence, however, is not consistent with this hypothesis. In the present study estrogen primed ovariectomized-adrenalectomized rats were administered p-chlorophenylalanine and were tested for lordosis behavior 66 and 70 hr later. Lordosis was not facilitated. The animals were then administered progesterone and retested at hour 74. PCPA inhibited progesterone-induced lordosis behavior in a dose dependent manner.

Maternal behavior in the rat: Aspects of concaveation and neonatal androgen treatment

Abstract Evidence is presented to show that maternal responsiveness of lactating females differs from concaveation-induced maternal responsiveness of gonadectomized male and female rats of the Long-Evans strain. When rat pups were placed in a runway extension of the home cage lactating females retrieved the pups to a significantly greater degree than did the concaveation treated animals. The present experiment failed to show significant differences in concaveation-induced maternal responsiveness in gonadectomized males, females and neonatally androgenized females.

Effects of genotype on differential behavioral responsiveness to progesterone and 5alpha-dihdroprogesterone in mice.

Thirty female CD-1 mice, 30 female Swiss-Webster mice, 45 hybrid female mice of the strain SWCD1F1, and 45 hybrid female mice of the strain CD1SWF1 were ovariectomized and administered estradiol benzoate once weekly for 6 weeks. Estrogen injections were followed 2 days later by injections of progesterone, dihydroprogesterone (DHP), or oil and the animals were tested for receptivity 7 hr later. Over the six tests, there was a progressive increase in the frequency of lordosis responses in all strains following progesterone treatment. However, lordosis scores varied widely across animals within strains. Following DHP treatment, lordosis frequency was not increased in the Swiss-Webster strain. Females in the other strains did show a progressive increase in lordosis frequency over weeks. The data indicate that the hybrid strains develop the potential to respond to DHP and thus behave like the CD-1 strain, suggesting that sensitivity to DHP is a dominant trait.

Adrenal mediation of estrogen-induced ejaculatory behavior in the male rat ☆

Abstract Testosterone propionate (TP) and estradiol benzoate (EB) were equally effective in maintaining the complete copulatory pattern in castrated male rats. In castrated, adrenalectomized rats, however, TP maintained the copulatory sequence while EB failed to maintain ejaculatory responses. Both steroids maintained mounting behavior and TP was more effective than EB in maintaining intromission responses in the adrenalectomized animals. It is suggested that adrenal androgens may mediate the effects of EB on ejaculatory behavior.