Influence of experiential factors and gonadal hormones on pituitary-adrenal response of the mouse to novelty and electric shock.

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Abstract
Plasma corticosterone elevations were shown to occur in response to exposure to a novel environment and to the delivery of painful stimulation, such as footshock. The effects of experience with these types of stimuli upon the responsivity of the pituitary-adrenal system were examined. When mice were subjected to repeated footshock, the adrenocortical response was increased. When animals were repeatedly shocked in a specific environment, the adrenocortical-stimulating properties of the situational stimuli were also elevated. Plasma corticosterone elevations in response to merely being placed in an experimental chamber were not affected by 10 exposures to the situation. Previous data showed that animals that had been shocked in one environment were generally more responsive to many types of stimulus changes. Such a pattern of results suggests that the pituitary-adrenal system is subject to sensitization processes and that the CNS substrate which controls its function is one that is normally involved with the production of states of arousal. This configuration of results was pronounced in the female mouse regardless of hormonal state, and was absent in the intact male. The results of studies with gonadectomized males suggested that testosterone inhibits sensitization.