NOISE STRESS AND INVITRO ADRENOCORTICAL RESPONSIVENESS TO ACTH IN WILD COTTON RATS, SIGMODON-HISPIDUS

Wild cotton rats, Sigmodon hispidus, were utilized in an attempt to clarify further the interaction of intermittent high-intensity noise with the hypothalamic-pituitary-adrenal axis. Animals were collected during 3-week periods in the spring and autumn of the year. Within seasonal groups paired adrenals from control animals and from animals exposed to recorded jet aircraft noise were either (a) incubated in the presence or absence of ACTH and analyzed for cAMP content as well as corticosterone secreted or (b) subjected to an initial incubation in the presence or absence of ACTH followed by a second incubation in the presence of ACTH after which corticosterone content of the incubation media was analyzed. During initial incubations glands from noise-exposed animals within both seasonal groups exhibited slight but insignificant elevations in basal corticosterone secretion rates as compared to their control counterparts. However, ACTH elicited a significantly smaller response in terms of corticosterone secreted in (a) the noise-exposed as compared to control groups within either season and (b) the autumn as compared to the spring control groups. Additionally ACTH induced significantly smaller cAMP accumulations in noise-exposed as compared to control animals. Analysis of ACTH-stimulated corticosterone secretion after preincubation in the presence or absence of ACTH indicated either similar significant increases in both the control and noise-exposed groups (preincubation without ACTH) or significantly greater responsiveness in the noise-exposed as compared to the control group (preincubation with ACTH). The data suggest the increase of a noise-related factor of unknown origin which has the ability to diminish the expression of ACTH upon the adrenal cortex. © 1978.