B. Marin

Effects of low stress during pregnancy on certain parameters of the offspring

In recent years the effect of intense stress applied during pregnancy has been studied. In this work, we exposed the mother to low immobilization stress throughout the entire pregnancy. This treatment that increased the sexual capacity in males had no detectable effects on the reproductive behavior of females. A positive role of this phenomenon in nature is suggested, as the offspring of stressed mothers would be more capable of facing difficult and selective environments.

Stress and sexual behavior in male rats

Abstract The relationship between sexual behavior and stress in male rats was investigated. Stress induction by psychophysical immobilization fo 3 hours along three days caused significant alterations of the different parameters which make up the sexual behavior of male rats. An extension of the stressing situation from 3 to 6 hours under the same experimental conditions produced very similar sexual disturbances. Our experimental results suggest that effects of acute stress on sexuality may be independent of time.

Sex difference in polyethylenglycol-induced thirst

The polyethylenglycol-induced thirst in male and female castrated rats has been studied. The polyethylenglycol (PG) increases the water intake more in females than in males. Estradiol benzoate and testosterone P. diminishes the amount of water drunk after PG treatment in the females, but not in the males.

Angiotensin-induced dringking: Sexual differences☆

The dipsogenic effect of Angiotensin-II (A-II) in relation to sexual variables was studied. It was found that Angiotensin-II administered SC constitutes a stimulus which induces more drinking in females than in males. Moreover, the adult females show maximum sensitivity to A-II during proestrus. The males and females castrated at birth, and females androgenized at birth, drink similar volumes of water after A-II SC injection. The pattern of stimulated intake is different in the two sexes, and appears to depend upon the development of the rats.

Circadian rhythms of plasma corticosterone at different times after induction of diabetes. Responses to corticoadrenal stimulation in light and dark phases

In this study we have tried to determine the effects of streptozotocin-induced (50 mg/kg) diabetes (15 and 30 day duration) on circadian rhythms of plasma corticosterone concentrations and on the responsiveness of the adrenal glands to exogenously administered ACTH at the time of maximum and minimum levels of plasma corticosterone. Rats were kept under controlled lighting 12h light/12h dark (12L/12D) and fed ad libitum. The corticosteroid circadian pattern in control (C) rats is characterized as one in which peak corticosterone concentrations occur at the beginning of the dark phase (activity period), with a decrease over the remainder of the 24h period. Circadian rhythmicity of plasma corticosterone concentration was absent in the diabetic rats 15 days after induction (D15 rats), with higher mean levels than the C. However, in the diabetic rats 30 days after induction (D30 rats) there is a recovery of this rhythm with similar acrophase and amplitude to the C rats. One hour after stimulation by ACTH (5 IU/kg) at the time of maximum and minimum levels of plasma corticosterone, the C rats showed similar plasma corticosterone levels. In the D15 rats, levels of corticosterone in the light phase one hour after ACTH administration were higher than in the dark phase; being lower than C in this phase. The loss of capacity to respond during the dark phase may be due to adrenal blunting in this phase with high levels of plasma corticosterone. In D30 rats, there is a more noticeable loss of capacity for adrenal response in the light than in the dark phase, with values lower than C and D15 rats in both phases. These findings suggest that the duration of diabetes has a significant role in both plasma corticosterone rhythms and adrenal sensitivity to ACTH administration.

Effects of inhibitors of the renin-angiotensin system on water intake after insulin administration

Male wistar rats drank in a dose-related manner, in response to 1 to 40 U/kg of i.p. insulin. Maximum intakes took place during the first 30 min after i.p. insulin administration, coinciding with the period of maximal drop of blood glucose. Plasma renin activity (PRA) in rats treated with i.p. insulin was higher than in basal conditions or after saline injection. Nephrectomy and adrenalectomy did not abolish insulin-induced drinking. A low dose of captopril (0.1 mg/kg s.c.) did not modify insulin-induced drinking, but a higher dose (10 mg/kg s.c.), or enalapril (0.5 mg/microgram s.c.), significantly increased insulin-induced drinking. Enhancement of insulin-induced drinking by s.c. captopril was not secondary to an increased diuresis. Captopril (50 micrograms i.c.v.) significantly reduced the cumulative water intake after i.p. insulin (20 U/kg i.p.) plus s.c. captopril (10 mg/kg). The blockade of central receptors for angiotensin II with sarile-AII (5 micrograms) significantly diminished insulin-induced drinking. It appears that the peripheral renin angiotensin system is not necessary for insulin-induced drinking but central angiotensin II plays an important role.

Effect of early pre- and postnatal acquired malnutrition on development and sexual behavior in the rat

In this paper we attempt to elucidate the effects on the rat offspring of undernourishment during pregnancy and lactation on the following parameters were examined: weight at birth and its evolution over a three-month period, sexual behavior of adult males, vaginal opening and sexual cycle of females, blood sugar, blood proteins, hematocrit, natremia, potassemia, body weight and weight of testicles, seminal vesicles and adrenal glands in males 5 months of age. Our results indicate highly significant decreases in body weight in experimental animals over a period of three months. Vaginal opening in experimental females is significantly delayed and their estrous cycle is shortened. Male sexual behavior shows decreases in neuromotor activity and prolongation of the refractory period in experimental male animals. Of the parameters monitored at 5 months of age, only blood sugar levels were significant decreased in experimental male rats. In view of these results, it can be concluded that in utero and lactation period malnutrition affects fundamental parameters of both development and reproductive function in the offspring.

Renin Dependence of Insulin-Induced Thirst

The influence of insulin on food intake has been amply studied. However there has been little work on the effect of this hormone in water intake. In 1964 Novin1 reported increased water intake due to insulin administration, separated from its effect on food intake. Booth and Brookover2 (1968), Spitz3 (1974) and Waldbillig and Bartness4 (1981) also found similar results of stimulation of thirst by insulin. Unpublished results by Fitzsimons reveal that i.p. insulin-induced drinking (IID) is abolished by nephrectomy. It could favour the possible participation of the renin-angiotensin system in this phenomenon. Waldbillig and Bartness4 found that i.p. insulin produced neither hypovolemia non plasmatic hyperosmolality, both conditions typified as thirst stimuli. On the contrary, animals presented hypervolemia and hypoosmolality.

Insulin stimulation of water intake in humans.

Drinking response to the intravenous administration of insulin (0.1 U/kg) was studied in 15 volunteers (eight males and seven females). Water intake was significantly higher after insulin than after saline administration during the 90-min period studied. Plasma glucose decreased significantly in individuals receiving insulin and the time of the maximum decrease (30 min) was concurrent with the beginning of water intake. Haematocrit values in the insulin-treated group were also significantly higher at that time. Plasma renin activity (PRA) after insulin administration was higher than under basal conditions or after saline injection. On the other hand, psychological responses indicated that insulin probably elicits thirst prior to the hunger which appears with hypoglycaemia. A possible role of endogenous insulin in meal-related thirst is hypothesized.

Effects of ovariectomy on the oxidative metabolism of the central nervous system and adrenal glands in female hamster (Mesocricetus auratus).

We have studied the influence of ovariectomy on the oxidative activity of hypophysis, hypothalamus, posterior cortex, septal area, amygdala and adrenal glands, in female hamsters, because their neuroendocrine behavior seems to differ from that of rats. Our results show a decreasing the O2 uptake in the hypothalamus and adrenal glands and an increase in the rest of the structures.