Sexual stimulation does not affect plasma LH nor testosterone levels in New-Zealand male rabbits

Young sexually naive (3-4 months) and sexually experienced (2-3 years) male rabbits were subjected to various sexual stimulation procedures. Blood samples were taken just before and 30 min after mounting (unreceptive females) or coitus (receptive females). Testosterone and luteinizing hormone were assayed using specific radioimmunoassays. Sexual stimulation did not affect postcoital testosterone and LH levels in naive and experienced males while in females LH levels were significantly increased. We may conclude that the postcoital neuroendocrine reflex which causes a massive release of pituitary LH in female rabbit does not exist in males.     

Diurnal variations of serum testosterone levels in intact and gonadectomized male and female rhesus monkeys.

A radioimmunoassay for serum testosterone which does not require chromatographic separation was used to measure the diurnal variations in intact and orchidecomized males and intact and ovariectomized females. The intact male rhesus monkey shows a distinctive diurnal variation in serum levels of testosterone characterized by lower values during the day and a marked increase in the early evening (1900-2200 hr). The testosterone levels remain high throughout most of the lights-off period in the intact male. In contrast to the intact male, the markedly lowered serum levels of testosterone in the orchidectomized male were higher during the day and consistently showed a nadir during the early evening (2000-2200 hr). The evening nadir of testosterone levels was 51.0% lower than the 24-hr mean whereas the maximum serum level was 46.4% higher. A similar circadian pattern of testosterone was seen in both the intact and ovariectomized females. The testosterone values were higher during the day and consistently showed a nadir during the early evening. These results suggest that the adrenal secretion of testosterone varies in a diurnal pattern characterized by an early evening nadir. This adrenal pattern is overshadowed by a much larger gonadal rhythm in the intact male.     

Subnormal serum testosterone levels in male internal medicine residents.

The consequences of sleep deprivation and stress in residency training have not been quantified. In the course of assembling a control group for other studies, we unexpectedly observed a significant (P less than 0.005) and marked depression of serum testosterone levels in healthy male internal medicine residents (means = 11.8 +/- 1.1 nmol/L, n = 7) compared with other hospital personnel (means = 20.6 +/- 5.3 nmol/L, n = 18). Testosterone concentrations in the two groups were entirely nonoverlapping, while luteinizing hormone levels were not significantly different. We conclude that the stress of residency training leads to a quantifiable depression of gonadal function, and that gonadal steroid concentrations may be useful in evaluating measures intended to reduce that stress.     

Effect of forebrain implants of testosterone or estradiol on scent-marking and sexual behavior in male and female rabbits

Chinning consists of rubbing the chin against an object, thereby depositing secretions from the submandibular glands. As mating, chinning is stimulated in male and female rabbits by testosterone and estradiol, respectively. To investigate the brain sites where steroids act to stimulate chinning and mating we implanted into the ventromedial hypothalamus (VMH) or the medial preoptic area (MPOA) of gonadectomized male and female rabbits testosterone propionate (TP; males) or estradiol benzoate (EB; females) and quantified chinning and sexual behavior. EB implants into the VMH or MPOA reliably stimulated chinning in females. Most of those implanted into the VMH and around half of the ones receiving EB into MPOA or diagonal band of Broca (DBB) showed lordosis. Chinning, but not sexual behavior, was stimulated in males by TP implants into the MPOA or DBB. Neither chinning nor mounting were reliably displayed by males following TP implants into the VMH. Results indicate that, in females, the VMH is an estrogen-sensitive brain area that stimulates both chinning and lordosis while the MPOA seems to contain subpopulations of neurons involved in either behavior. In males, androgen-sensitive neurons of the MPOA, but not the VMH, are involved in chinning stimulation but it is unclear if these areas also participate in the regulation of copulatory behavior.     

Effect of forebrain implants of testosterone or estradiol on scent-marking and sexual behavior in male and female rabbits

Chinning consists of rubbing the chin against an object, thereby depositing secretions from the submandibular glands. As mating, chinning is stimulated in male and female rabbits by testosterone and estradiol, respectively. To investigate the brain sites where steroids act to stimulate chinning and mating we implanted into the ventromedial hypothalamus (VMH) or the medial preoptic area (MPOA) of gonadectomized male and female rabbits testosterone propionate (TP; males) or estradiol benzoate (EB; females) and quantified chinning and sexual behavior. EB implants into the VMH or MPOA reliably stimulated chinning in females. Most of those implanted into the VMH and around half of the ones receiving EB into MPOA or diagonal band of Broca (DBB) showed lordosis. Chinning, but not sexual behavior, was stimulated in males by TP implants into the MPOA or DBB. Neither chinning nor mounting were reliably displayed by males following TP implants into the VMH. Results indicate that, in females, the VMH is an estrogen-sensitive brain area that stimulates both chinning and lordosis while the MPOA seems to contain subpopulations of neurons involved in either behavior. In males, androgen-sensitive neurons of the MPOA, but not the VMH, are involved in chinning stimulation but it is unclear if these areas also participate in the regulation of copulatory behavior.     

Effect of long-term pinealectomy on serum LH levels and on cerebral serotonin metabolism in adult male rats

Two months after pinealectomy carried out in adult male rats previously exposed to a long photoperiod (L:D 14:10) during 10 weeks, the weight of seminal vesicles significantly increased in comparison with Sham-operated animals. Nevertheless, the weights of testes and ventral prostate did not change significantly. The serum LH concentration increased significantly by pinealectomy. The levels of serotonin and 5-hydroxiindolacetic acid significantly decreased in the hypothalamus and midbrain after pinealectomy.     

Effect of estradiol & testosterone on the pituitary prolactin levels in developing male & female rats

Testosterone priopionate (TP) or estradiol-17 beta (E2) were injected into male and female rats from day of birth to 15 days of age to determine the effect of these steroids on the pituitary prolactin (PRL) level in developing rats. Animals were autopsied on Days 5, 7, 10, 14, 17, 22, 25, 30, 37, 45, 52, and 60 and pituitary PRL estimated by radioimmunoassay. Neonatal administration of TP or E2 markedly increased PRL content in male rats. The peak of PRL was advanced to Days 14 and 23, respectively, in E2- and TP-treated groups. The content of pituitary PRL declined sharply and values increased again by Day 52 in TP-treated rats and Day 37 in E2-treated rats. In the female rat both the steroids advanced the time of PRL peak. Peaks were observed on Days 22 and 30, respectively. Although PRL content declined following these peaks, values remained at a significantly higher level than normal. These results suggest that mechanisms controlling the PRL secretion are functional during the neonatal period. It is also suggested that TP acts to increase PRL levels by 1st being converted to E2.     

Effect of coitus on sperm transport and fertilization in rabbits

The number of spermatozoa into the Fallopian tubes and levels of in vivo fertilization were measured following different treatment. The results show that copulation by the artificially inseminated animal has a strong influence on the transport of the rabbit spermatozoa and "in vitro" fertilization. This constitutes some more evidence about the physiological role played by the utero-tubal junction.     

Intracerebroventricular injection of neuropeptide EI increases serum LH in male and female rats

Melanin concentrating hormone (MCH) precursor-derived neuropeptide EI (NEI) has not yet been extensively studied. The aim of this study was to determine the effect of neuropeptide EI on serum levels of LH in normal male rats and chronically ovariectomized (CHR-OVX) female rats treated with estrogen benzoate (EB) and with a low dose of progesterone. The peptide, administered intracerebroventricularly in male and chronically ovariectomized female rats, increased LH serum levels compared to the controls injected with artificial cerebrospinal fluid. It is important to note that there is some relation between neuropeptide EI-melanin concentrating hormone and alpha-melanocyte stimulating hormone (alpha-MSH) indicating that all three peptides are associated in a complex inter-relationship. Therefore, the question that arises is if neuropeptide EI could also be related with the receptors for melanin concentrating hormone or alpha-melanocyte stimulating hormone.     

Acute effects of testosterone on serum PGE2 levels in male dogs

Serum prostaglandin levels are influenced by testosterone. To test the hypothesis that the effect of testosterone is mediated through the prostate gland, testosterone was given acutely to intact and to prostatectomized male dogs. Intact dogs responded to testosterone with an abrupt, transient rise in plasma PGE2 levels; prostatectomized dogs did not respond. We conclude that testosterone has an acute effect on the prostate gland which results in release of PGE2 into the blood stream.     

Effect of active immunisation against testosterone-3-BSA on circulating levels of testosterone, LH, prolactin and testosterone antibody titre in the male rat

Male Sprague-Dawley rats were actively immunised against testosterone-3-bovine serum albumin (T-3-BSA) and on appearance of detectable anti-testosterone antibodies, elevated serum testosterone and LH concentrations were observed. These concentrations reached values of >28 μg/100ml testosterone and 16 μg/100ml LH in some animals after 5 months of immunisation. The corresponding prolactin values did not appear to differ significantly from controls. The circulating bound testosterone fraction as determined by equilibrium dialysis, rose from 65.0 ± 2.75% before immunisation to 98.7 ± 0.75% in those animals possessing high titre antisera. This entailed a nett $\text{decrease}$ in the concentration of unbound steroid from 144 ± 49 ng/100 ml to 78 ± 25 ng/100ml.     

The effects of indomethacin on plasma LH levels in female and male deermice ( )

The purpose of this investigation was to determine (1) the approximate time of the preovulatory LH rise in cyclic deermice, (2) the effect of indomethacin administration on plasma LH levels during the expected preovulatory LH rise, and (3) the effect of indomethacin administration on plasma LH levels in castrated male deermice. The data indicate that the preovulatory LH rise occurred at about 2200 h on proestrus and that indomethacin pretreatment significantly reduced plasma LH levels during that time. In addition, indomethacin significantly reduced plasma LH levels in castrated male deermice. We conclude that plasma LH levels remain low throughout the estrous cycle with the exception of the preovulatory “surge”, that plasma LH levels in deermice are comparable to those reported for the rat, and that indomethacin pretreatment reduced plasma LH levels during periods when they were expected to be elevated (in castrated males and during the expected preovulatory LH rise in female deermice). The data are consistent with the hypothesis that the effect of indomethacin on plasma LH levels is due to an inhibitory effect on hypothalamic PG biosynthesis.