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Glucocorticoid receptors in human peripheral blood mononuclear cells in relation to age and to sport activity.

Glucocorticoid receptors (GR) are ubiquitous molecules and are present also in the hippocampus and in several other nervous and immune tissues. Peripheral blood mononuclear cells (PBMCs) are a good model for studies of GR in humans. Glucocorticoids are important for maintaining cellular and humoral homeostasis and are key mediators of neuroendocrine-immune regulatory interactions. The increase of cortisol is immunosuppressive and reduces GR concentration both in nervous and immune systems. Variation of glucocorticoids in healthy aged subjects and athletes has been shown. Prompted by these results, we have investigated in man a possible relationship between GR binding capacity in the PBMCs and age, in relation also to plasma testosterone and cortisol. The same parameters have been examined in a group of soccer players for comparison with the sedentary group. GR binding capacity was higher in younger subjects than in older ones, and lower in the group of athletes than in the younger and older sedentary subjects. In the sedentary group a negative correlation was present between GR binding capacity and age. Plasma cortisol was higher and testosterone lower in the athletes; they were negatively correlated in athletes and positively correlated in the sedentary subjects. The results for athletes agree with their lower anabolic/catabolic balance. The mechanism of reduced GR levels in relation to age and sport activity could involve a loss or an involution of receptor synthesis. However other possibilities, such as altered distribution of lymphocyte subpopulations with different receptor concentrations and with different cytokine production, cannot be excluded. Several neuroendocrine-immune interactions could be responsible for reduced GR levels with age and sport activity in man.

Odour of male and female rats changes hypothalamic aromatase and 5α-reductase activity and plasma sex steroid levels in unisexually reared male rats

Male rats between 25--65 days of age were reared under four different social conditions: (1) In cohabitation with only males; (2) as in (1), but exposed to bedding from a cage containing other males; (3) as in (1), but exposed to bedding of females; (4) in cohabitation with both males and females. At 65 days of age the animals were killed and analyzed for plasma levels of testosterone and estradiol and in vitro studies were undertaken of hypothalamic testosterone metabolism. Males reared in absence of females showed lowered testosterone and estradiol plasma concentrations and increased hypothalamic aromatase and 5 alpha-reductase activity compared to heterosexually reared males. The effects of cohabitation with males only were counteracted by exposure to bedding of other males or of females suggesting an importance of odoriferous stimuli associated with sexually mature males and females during the sexual maturation of the male rat.

Effect of androgens on structure and rate of crowing in the Japanese quail (Coturnix japonica)

To study the influence of testosterone (T) on crowing in male Japanese quails, we combined hormonal and photoperiod manipulations of circulating androgens with a detailed analysis of the acoustic parameters of crows and of male courtship patterns. The structure of crowing was directly affected by T: high-androgen males uttered longer and lower-pitched calls than the others, call rate at dawn being related to androgens by a minimum threshold function. High- and low-callers, two consistent categories over many days, differed in their sexual performance: high-callers performed more courtship than low-callers, but there was no difference in attempted mating. Crowing is discussed as a potential target of sexual selection because, like a song, it is androgen-dependent, highly variable among individuals, and plastic in its structure at the beginning of the reproductive season.

Changes in brain serotonin and 5-hydroxyindolacetic acid levels in the rabbit following tonic immobility

The effect of tonic immobility on serotonin (5-hydroxytryptamine, 5-HT) and on 5- hydroxyindolacetic acid (5-HIAA) levels in different brain areas has been investigated, following two different schedules of treatment. The massed treatment consisted of a series of consecutive trials up to 15 min, the spaced treatment in 4 series of trials within 24 hours. Massed treatment produced a decrease in 5-HT in the mesencephalon and of 5-HIAA in the pons-medullary area, but similar changes were also elicited in animals treated with the procedure of induction not followed by immobility. The spaced treatment, which resulted in a potentiation of the immobility duration, i.e., sensitization, produced a reduction of 5-HT levels in the mesencephalon and of 5-HT turnover in the striatum. The procedure of the induction per se acts preferentially on 5-HIAA by increasing its levels. In the striatum, which appears selectively responsive to the spaced treatment of immobility, a negative correlation has been found between serotonin levels and immobility duration. Results suggest that elicitation of tonic immobility is associated with reduced levels of 5-HT in the brain.

The effect of medial preoptic-anterior hypothalamic lesions on testosterone plasma levels and testosterone conversion in the hypothalamus of male rats.

Male Wistar rats were submitted to bilateral high frequency lesions in the medial preoptic-anterior hypothalamic area or to sham procedure. The behavioral effect of the lesions was observed and plasma testosterone (T) and estradiol (E2) were measured by radioimmunoassay. In vitro metabolism of T was studied in the hypothalamus. Lesions produced a permanent deficit in male sexual behavior, an increase of plasma T and E2, and of hypothalamic T aromatization, and a decrease of T conversion to 5 alpha-dihydrotestosterone (DHT).

Effect of Castration on Hypothalamic Testosterone Metabolism in the Male Rat

In vitro studies were performed of hypothalamic testosterone (T) metabolism 30 days after castration of adult male rats. No changes were seen in T conversion into dihydrotesterone and estrogens in the castrated rats. Plasma T levels were decreased while plasma estradiol concentrations did not differ from those of intact controls. It was suggested that the hypothalamic T metabolism probably is not androgen dependent.

Behavioural and hormonal effects of captivity on the immobility reaction in crested newts (Triturus cristatus carnifex)

Abstract The immobility reaction in Triturus cristatus carnifex was analyzed in behavioural and endocrine aspects in relation to captivity. The behavioural effect consisted in a decrement of immobility latency in males. In females testosterone (T) and estradiol (E) plasma levels were lowered, while in males the T/E ratio was enhanced and E lowered. Captivity also abolished the correlation between hormonal and behavioural values.

Exposure to Odour During Development and Hypothalamic Metabolism of Testosterone

Sex hormones influence many aspects of male behaviour in vertebrates. In the same time sociosexual stimulation can modulate the endocrine activity of the male. In particular copulation increases testosterone (T) circulating levels in a variety of species including guinea pig (Harding and Feder 1976), rat (Purvis and Haynes 1974, Kamel et al. 1975, 1977) and mouse. However, sexual contact with the female is not essential to induce these changes. Purvis and Haynes (1974) and Kamel et al. (1975) report that mere exposure to a female increases sexual hormones release in the male rat. The hormonal status of the female is not apparently critic: exposition to oestrous, anoestrous, ovariectomized females yields similar effects (Kamel et al. 1975, 1977). Female odour by itself is able to increase T and LH levels in the male mouse, hamster and rat (Maruniak et al. 1978, Macrides et al. 1975, Dessi-Fulgheri and Lupo 1982).

Sexual behaviour in castrated male rats and gonadal steroid circulating levels

Abstract Circulating testosterone (T) and estradiol-17β (E2) were measured in a group of 33 castrated male Wistar rats with previous sexual experience. T and E2 were determined by R.I.A. before and after a sexual activity test done 12 days after castration. The main results of the study are a lack of correlation between hormones studied and sexual performance, and a significant increase, after the behavioural test, of T circulating levels in the castrated males that were sexually active. This result suggests that also in the intact male, to understand the relationship between T secretion and sexual behaviour, not absolute value of T levels but individual changes should be taken into consideration.