Biomedical subjects

D B Yelvington

Publications and source records attributed to D B Yelvington.

6 recordsLinked to original sources

PubMed1989

Prolactin and corticosterone response to repeated footshock stress in male rats.

The prolactin (PRL) and corticosterone (CORT) responses to footshock stress were measured in rats after the first, fifth, and 57th exposure to the stress procedure. No reduction in the PRL or CORT responses was seen after repeated application of the footshock stress and the animals showed similar behavioral responses throughout. These results indicate that the hormonal and behavioral responses to footshock stress are not attenuated after an animal has been repeatedly exposed to the stress.

Animals↗

PubMed1987

Effect of illness on hormonal response to footshock stress.

The corticosterone (CORT) and prolactin (PRL) responses to 1.0 mA of footshock were measured in healthy rats and rats with pneumonia. No differences in basal PRL levels were seen, but basal CORT levels were significantly increased in the sick animals. Healthy rats showed a significant increase in both PRL and CORT after receiving footshock whereas the sick rats showed no changes. The adapative value of the current findings are unclear at this time.

Animals↗

PubMed1986

Avoidance behavior and plasma prolactin levels in lergotrile mesylate treated rats.

We have previously shown that psychological factors play a major role in control of prolactin (PRL) secretion, and that PRL increases during shock-motivated avoidance conditioning. In the present studies, we examined whether we could attenuate acquisition performance by suppressing the PRL increase during avoidance testing. Rats were tested daily in a shuttle box. They were presented with a light stimulation followed by an electric footshock. During each trial, the rats were given the opportunity to escape the footshock by moving to a safe side of the box. Movement to the appropriate location after the warning signal (light) begins, but before the onset of the footshock, constitutes a conditioned avoidance response (CAR). Experimental rats were fitted with an intraperitoneal osmotic minipump which delivered lergotrile mesylate (LM), 0.69 mg/kg/day. Blood samples were collected from an indwelling cannula and analyzed by radioimmunoassay. Administration of LM blocked the PRL increase that occurred during early avoidance testing, but did not alter the acquisition of a CAR. These data do not support the idea that PRL acts to facilitate acquisition of avoidance behavior.

Animals↗

PubMed1985

Plasma prolactin levels during conditioned avoidance behavior in rats.

In these experiments, we examined the prolactin (PRL) response during the acquisition of a conditioned avoidance response (CAR). Rats were tested daily in a two-way shuttle box. They were presented with a light stimulation followed by an electric footshock. During each trial period, the rats were given the opportunity to escape the footshock by moving to a safe side of the box. Movement to the appropriate location after the warning signal (light) begins, but before the onset of the footshock, constitutes a CAR. Blood samples were collected from an indwelling cannula and analyzed by radioimmunoassay. PRL levels increased during early acquisition testing, when the rats had not learned to avoid the shock. After one week of testing, acquisition performance increased considerably (70% CARs) while PRL levels remained unchanged. Thus, we were able to show that as rats learned to modify their behavior in response to a stressful situation, they could also modify their PRL response to the stressor.

Animals↗

PubMed1985

Habituation of the prolactin response in rats to psychological stress.

It is well known that stress is a stimulant for prolactin release. However, relatively few studies have investigated the role of psychological factors in prolactin secretion, and investigators have typically used one-time exposure and a single collection period in their studies. In our studies, attempts were made to carefully characterize the prolactin response to different psychological stressors by serially sampling blood from an indwelling cannula and to determine if repeated exposure to the stressor leads to habituation of the prolactin response. Exposure of the male rats to different novel situations such as being placed in a new cage, being placed on a platform in water, or being handled resulted in increased prolactin levels. As the rats habituated behaviorally to repeated exposure to similar situations, the prolactin response also attenuated. These findings show that psychological factors do play a role in influencing prolactin secretion and are consistent with the idea that as the psychological stress imposed by a stimulus becomes habituated, the prolactin response to that stimulus also becomes habituated.

Animals↗

PubMed1984

Effect of corticosterone on the prolactin response to psychological and physical stress in rats.

Both corticosterone and prolactin (PRL) levels increase in response to stress. In these studies we examined the effect of corticosterone on the PRL response to both physical (footshock) and psychological (novel environment) stress. Three groups of rats were used: sham adrenalectomized (SHAM), adrenalectomized (ADX), and adrenalectomized with corticosterone replacement (ADX+CORT). The corticosterone-treated animals received 80 micrograms corticosterone/ml drinking water. Blood samples were drawn via an indwelling cannula and PRL values determined using radioimmunoassay. ADX rats showed a consistently greater PRL response to being placed on a platform above water (novel environment) or when receiving intermittant footshock than did ADX+CORT rats. The PRL response of the latter group was similar to that of the SHAM animals. These findings indicate that corticosterone levels of an animal can significantly attenuate the magnitude of the PRL response to both physical and psychological stress. These findings further emphasize that the PRL response to stress is dependent not only upon the immediate action of the stressor, but also the prior stress history of the animal.

Adrenalectomy↗