Effects of differential mating stimulation on the onset of prolactin surges in pseudopregnant rats.

In the female rat, stimulation of the uterine cervix (CS) during mating or by artificial means induces daily diurnal and nocturnal surges in prolactin (PRL) secretion which, in the absence of fertilization, result in an 12-day anestrous period called pseudopregnancy (PSP). The amount or type of mating stimulation received by the female during mating determines whether or not PSP occurs, but it has not yet been determined whether different amounts of mating stimulation can alter the time of onset of PRL surges. The present studies examined the latency in days to the first nocturnal PRL surge following mating.

Metabolism of dihydrotestosterone to 3 alpha-androstanediol in brain and plasma: effect on behavioural activity in female rats.

Six experiments were carried out to determine whether dihydrotestosterone (5 alpha-androstan-17 beta-ol-3-one; DHT) acts to inhibit oestradiol (OE2)-induced lordosis behaviour after its metabolic conversion to 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-androstanediol, 3 alpha-Adiol). In experiments 1 and 2, ovariectomized rats were treated with several doses of DHT or 3 alpha-Adiol, injected with OE2 and progesterone, and tested for lordosis responsiveness. Significant inhibition of lordosis occurred after a dose of 3 alpha-Adiol which was approximately threefold less than the effective DHT dose.

Acute luteinizing hormone and prolactin responses to paced mating stimulation in the estrous female rat.

The present experiments sought to characterize the particular stimuli received during mating in the female rat which induce acute increases in luteinizing hormone (LH) and prolactin (PRL) following copulation. Comparisons were made between cycling females mated on the evening of proestrus in partitioned chambers in which spontaneous patterns of approach/withdrawal toward the male served to pace copulatory stimulation (paced), in non-partitioned chambers in which female regulation of intervals between copulatory mounts was prevented (non-paced), or under conditions in which they received mounts-without-intromission (mounts-only). Frequent blood samples were withdrawn via surgically implanted intra-atrial catheters.

Stress and ACTH increase circulating concentrations of 3 alpha-androstanediol in female rats.

The present experiments were carried out to determine what physiological conditions are responsible for the acute increases in serum levels of 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-androstanediol, 3 alpha-Adiol) which are seen in the intact estrous female rat within 15-30 min after mating. Blood samples were obtained from proestrus rats immediately before and 20 min after injection of exogenous hormones or initiation of stress procedures, and plasma concentrations of 3 alpha-Adiol and/or progesterone (P) were measured in these samples by RIA. Intravenous injections of ovine LH (5, 15, or 45 micrograms) or saline resulted in equivalent significant increases in plasma 3 alpha-Adiol 20 min after injection.

Prenatal and neonatal testosterone exposure interact to affect differentiation of sexual behavior and partner preference in female ferrets.

Implanting testosterone (T) subcutaneously over Postnatal Days 5-20 masculinized sexual behavior, reduced proceptive responsiveness, and shifted sexual preference more readily in male than in female ferrets gonadectomized on Day 5. This enhanced sensitivity of males to neonatal T was best duplicated in females exposed transplacentally to T over Embryonic Days (E) 27-39 (41-day gestation) and injected at birth with T (2.5 micrograms sc in oil: 10% ethanol).