Pituitary—adrenal responsiveness of mothers to pups in mice of two inbred strains

Abstract

Lactating A/J but not C57BL/6J mice had higher plasma levels of corticosterone if their pups were removed, shocked, and then returned in a wire-mesh basket than they did if their pups were removed and an empty basket was returned. The same results were obtained when mothers reared and were tested with pups of the nonmaternal strain. Nulliparous females of both strains showed no greater corticosterone response to shocked pups in a wire basket than they did to the basket alone. Finally, lactating A/J but not C57BL/6J mice had higher plasma levels of corticosterone if they and their litters were undisturbed than if their pups were removed 3 hr 15 min earlier. These results indicate that: (1) stimuli from inaccessible distressed pups can activate the pituitary—adrenal system of lactating mice; (2) interstrain variability observed in this response was due to a difference in maternal genotype; (3) this response does not appear to be common to females of all reproductive states; (4) direct contact with undisturbed pups can also stimulate increased maternal pituitary—adrenal activity in A/J mice.