Role of the adrenal gland and adrenal-mediated chemosignals in suppressionof estrus in the house mouse: The Lee-Boot effect revisited

Mature female mice, grouped in the absence of a male stimulus, exhibit a su ppressed estrous cycle (the so-called Lee-Boot effect). We have designed a series of experiments to elucidate the involvement of the adrenal gland in this phenomenon. Our initial results indicate that adrenalectomized mice ex hibit a regular estrous cycle in either isolated or grouped conditions. A s ingle, intact mouse caged with five adrenalectomized females showed repeate d normal cycles. When the urine samples from group-caged intact mice or gro up-caged adrenalectomized mice were applied to the external nares of singly caged females, estrous cycles were inhibited in the animals receiving urin e from the intact mice but not from the adrenalectomized mice. In addition, corticosterone therapy restored the function of estrus suppression in grou ped, adrenalectomized mice. We had previously shown that the urinary excretion of several volatile comp ounds (2-heptanone, trans-5-hepten-2-one, trans-4-hepten-2-one, pentyl acet ate, cis-2-penten-1-yl acetate, and 2,5-dimethylpyrazine) was adrenal media ted (Science 1986; 231:722-725). A further testing of these compounds in re lation to estrus suppression has now revealed that a mixture of these compo unds is effective, but removing 2,5-dimethylpyrazine from the mixture aboli shed the biological response. The overall results of this study show conclu sively an important role of the adrenal gland and adrenal-mediated urinary metabolites in estrus suppression.