Biomedical subjects

H G van Oyen

Publications and source records attributed to H G van Oyen.

12 recordsLinked to original sources

PubMed1985

Age effects on passive avoidance behavior of vasopressin-deficient Brattleboros.

Experiments in which vasopressin-deficient Brattleboros were tested in a passive avoidance procedure have yielded contradictory results. Some investigators observed the passive avoidance behavior of these subjects to be inferior to that of normal controls, while others failed to observe such differences. Inspection of the literature suggested that age differences between subjects which participated in these experiments might be responsible for the discrepancy. In the present experiment, HO-DI and HE Brattleboro rats of different ages were tested in the standard passive avoidance task. Passive avoidance performance of HO-DIs was, indeed, influenced by the age of the subject at the time of testing; HO-DIs reentered the shock compartment sooner than HE at 35 days, but later than HE at 120 days. There was no difference between the two groups of subjects at 60 days. The percentage of HO-DIs which reentered the shock compartment on the post-shock trial decreased with increasing age.

Age Factors↗

PubMed1984

The pituitary-adrenocortical system is not involved in the sex difference in passive avoidance.

UNLABELLED: The hypothesis that sex differences in passive avoidance are related to the sex difference in the pituitary-adrenocortical system was studied. A high dose of dexamethasone (500 microg/kg body weight) was injected in male and female rats in order to suppress the activity of the pituitary-adrenocortical system. Dexamethasone treated animals and controls were tested for retention of passive avoidance at one of 4 different intervals after punishment. The percentage of females re-entering the compartment in which they were previously shocked was significantly higher than the percentage of males, after a retention interval of 60 minutes, but not after an interval of 0 minutes or 15 minutes (Experiment 1). Dexamethasone did not affect this pattern of sex differences. The same sex difference was found after an interval of 24 hours (Experiment 2), and again dexamethasone had no effect on it. However, in males a state-dependent effect of dexamethasone treatment was found in Experiment 2 when animals were given two injections of either dexamethasone or saline, one before the learning trial and one before the retention trial. Within the groups of males given two different injections (Dex-Sal and Sal-Dex) a higher percentage re-entered the shock compartment, when compared with the groups of males given the same injection twice (Sal-Sal and Dex-Dex). CONCLUSIONS: (1) A sex difference in passive avoidance apparently occurs after a certain interval during which the animals are not disturbed. (2) This sex difference does not depend on the integrity of the pituitary-adrenocortical system. (3) State-dependency was observed in males only, indicating that changes in the pituitary-adrenocortical system, as a consequence of dexamethasone treatment, may have a more important stimulus value in males.

Adrenocorticotropic Hormone↗

PubMed1983

Failure of dexamethasone to influence sex differences in acquisition of discriminated lever press avoidance.

Discriminated lever press avoidance was used to test the hypothesis that higher plasma levels of pituitary-adrenocortical hormones in female rats can be held responsible for the superior active avoidance of female as compared to male rats. Male and female rats were administered dexamethasone (500 microg/kg body weight) during 4 days of avoidance acquisition and 1 additional day of extinction. This treatment resulted in a strong suppression of the pituitary-adrenocortical activity in both sexes. The corticosterone plasma level was very low, the adrenal weight was significantly reduced, but the pituitary weight was not affected. In other words, animals treated with dexamethasone were exposed to the lever press avoidance situation without a reactive pituitary-adrenocortical system. Under these conditions, sex differences in behavior were not affected and, therefore, the hypothesis that sex differences in pituitary-adrenocortical hormone levels contribute to sex differences in active avoidance, was not confirmed.

Adrenal Glands↗

PubMed1983

Behavioural changes following lesions of the orbital prefrontal cortex in male rats.

Bilateral lesions were made, confined to the orbitofrontal part of the prefrontal cortex (OF) of male WEZOB rats at 3 different ages (30, 45 and 60 days) and behavioural changes were studied in adulthood. In a test situation for intermale aggression OF-lesioned animals showed a higher level of aggression than their control-operated opponents. Such changes were not witnessed in encounters with male rats of the less aggressive Wistar strain which emphasizes the importance of the choice of the opponents in tests for agonistic behaviour. OF lesioning did not interfere with male sexual behaviour. When tested in an open field, activity scores of OF-lesioned animals exceeded those of the control group. OF lesioning resulted in a slight but significant long-term weight reduction, 2-3 months following surgery, in comparison with the control group. However, a severe reduction in food intake (aphagia), immediately after the operation, was not observed. Increase in both aggression and locomotor activity was seen in all 3 age groups, and data do not support the hypothesis that sparing of function had occurred in the 30-day operates, as compared with the 60-day operates. However, the duration of allogrooming bouts per approach in the social agonistic situation did show a pattern depending on the lesion momentum: prepubertal OF lesions resulting in less frequent approaches and grooming bouts of longer duration. These findings are explained in terms of perseverative tendencies following OF lesions.

Aggression↗

PubMed1982

Sexual behavior in female rats born in all-female litters.

Females born in all-female litters and females stemming from predominantly male litters were compared for masculine (mounting) and feminine sexual behavior (lordosis) under various dosages of estradiol followed by progesterone and under testosterone stimulation. Estradiol did not affect mounting levels in these groups. A critical dose level was established at 0.25 mg/animal of estradiol for both groups with respect to receptive behavior. Testosterone treatment reliably stimulated mounting in these females, but no differences were determined with respect to the litter composition in utero. The results are considered as a critical and negative finding with regard to the possibility that testosterone stemming from male littermates in utero affects the female's sexual development.

Animals↗

PubMed1982

Behavioral consequences of agonistic experience in rats: sex differences and the effects of testosterone.

The effects of winning or losing on subsequent aggressive behavior in male and female rats were studied. By using three strains of rats with different levels of aggression, a procedure was developed to create winners and losers. Subsequently, winners were tested against losers. Behavioral analysis of all tests enabled a thorough study of these processes and of their consequences. The results indicate that significant and relatively permanent behavioral changes are induced in intact and castrated, testosterone-treated males but not in females. The results suggest that behavioral inhibition is a specific characteristic of the male's agonistic behavioral repertoire.

Aggression↗

PubMed1981

Suppression of active sleep by chronic treatment with chlorimipramine during early postnatal development: effects upon adult sleep and behavior in the rat.

In an attempt to study the possible role of active sleep in brain development, male rats were injected twice daily with chlorimipramine, a potent monoamine reuptake blocker, from 1 week to 3 weeks of postnatal age. AS was reduced to less than 10% of total sleep time, the level found in mature rats. Most of the AS reduction was compensated for by quiet sleep but a slight increase in wakefulness also occurred, owing to brief interruptions of sleep at times when AS was expected. In adulthood, the AS-deprived rats showed a higher percentage of AS than did the controls, due to an increase in frequency and duration of AS epochs. Moreover, many of the epochs contained abnormally frequent and strong jerky body movements and rapid-eye-movements, reminiscent of neonatal AS patterns. In addition, the amplitude of hippocampal theta waves during AS was greater than in control rats. The chlorimipramine-treated rats also showed behavioral abnormalities in later life. On the open field test exploratory behavior was much reduced, while increased rearing and defecation occurred. Masculine sexual performance was severely deficient, primarily due to the low level of intromissions and ejaculations. Experimental animals performed less efficiently than controls on a temporal learning task (differential reinforcement of low response rate) and responded more rapidly on a spatial task (left-right alternation learning). These results demonstrate that early interference with the functioning of monoaminergic systems can have long-lasting physiological and behavioral consequences. Furthermore, they are consistent with the hypothesis that AS is an important factor in normal brain development.

Aggression↗

PubMed1981