THE MODULATION OF PLASMA BETA-ENDORPHIN LEVELS AND EXPLORATORY BEHAVIOR AS A FUNCTION OF CONDITIONS OF STRESS
The present study investigated the modulation of plasma beta-endorphin levels and exploratory behavior as a function of conditions of stress. The hypotheses being considered were: Exposure and stress will (1) educe high levels of plasma beta-endorphin; (2) affect exploratory behavior in the open field apparatus as seen in square crossing behavior; (3) affect exploratory behavior in the open field apparatus as seen in freezing behavior.^ Mice were used as subjects and were exposed to two conditions of stress--foot shock with escape and foot shock which was inescapable. Animals in the escape condition were required to jump through a hole in a partition to terminate the foot shock. Successful acquisition of this escape learning was achieved by all of the animals in this condition. The yoked inescapable shock animals received the same frequency, duration, and intensity of foot shock, but were not permitted any opportunity to terminate the foot shock.^ Following the eight day conditioning period, the animals were exposed to the buzzer signal only and received no foot shock. They were placed in an open field apparatus which was equipped with the buzzer signal. Observation was made of the exploratory behavior of each animal in the open field apparatus equipped with the buzzer signal which followed the identical temporal pattern used in the original conditioning. At the end of the exploratory session, the animal was immediately decapitated and trunk blood was collected for the beta-endorphin assay.^ The results of this study indicate that animals exposed to the escape contingency evidenced the highest plasma beta-endorphin levels with no significant effect on exploratory behavior. Whereas, animals exposed to inescapable shock evidenced significant elevation of plasma beta-endorphin levels and a significant deficit in exploratory behavior when compared with control animals. These findings were unexpected and demonstrated a role for beta-endorphin in the arousal to respond to stress rather than the analgesic effect described in earlier studies. It further suggests that high plasma beta-endorphin levels are not associated with deficits in exploratory behavior. These findings support the view that a failure to release beta-endorphin may be involved in poor adaptive functioning as seen in exploratory behavior deficits. (Abstract shortened with permission of author.) ^
SNYDER, MARGARET TURNER, "THE MODULATION OF PLASMA BETA-ENDORPHIN LEVELS AND EXPLORATORY BEHAVIOR AS A FUNCTION OF CONDITIONS OF STRESS" (1984). ETD Collection for Fordham University. AAI8506361.