Stress or acute adrenocorticotrophin treatment suppresses LHRH-induced LH release in the ram.

This study examined the effects of varying treatment durations and doses of adrenocorticotrophin (ACTH) as well as restraint stress on the LH response to exogenous LHRH. Injection of 80 i.u. of a concentrated ACTH preparation at 11, 6, 3 or 1.5 h before LHRH administration was effective in suppressing the LH response. Injection of 40, but not 20 or 10, i.u. ACTH 3 h before an LHRH challenge inhibited the magnitude of the LH response, while cortisol values did not vary between ACTH doses. Injection of 200 micrograms of synthetic ACTH1-24 also resulted in a reduced LH response when given 3 h before LHRH. Restraint stress caused elevated corticosteroid levels and reduced LHRH responsiveness. The results of this study suggest that stress may cause an inhibition of pituitary gland ability to respond to LHRH by way of an hormonal component of the adrenocortical axis. A glucocorticoid-independent mechanism may be involved.