Circulating LH levels and the response to exogenous GnRH in the common mole-rat: Implications for reproductive regulation in this social, seasonal breeding species

The effects of breeding season and reproductive status on male and female r eproduction were investigated in the common mole-rat, Cryptomys hottentotus hottentotus, a cooperatively breeding rodent which exhibits a unique combi nation of seasonal breeding and a reproductive division of labor. Pituitary function was examined by measuring the luteinizing hormone (LH) responses to single doses of 2 mu g exogenous gonadotrophin-releasing hormone (GnRH) and physiological saline in 69 males and 58 females from 35 wild-caught col onies. Neither males nor females exhibited any apparent manifestation of se ason on basal LH concentrations or an pituitary sensitivity to stimulation by exogenous GnRH. The continuance of reproductive function during the nonb reeding period is essential in common mole-rat males and females, as this p eriod coincides with the period of maximal dispersal opportunity in the win ter rainfall area they inhabit, Normal circulating levels of reproductive h ormones in dispersing animals may aid intersexual recognition, assist pair- bond formation, and thus prime animals for independent reproduction. Circul ating basal concentrations of LH as well as LH levels measured in response to a single exogenous GnRH challenge were not significantly different betwe en the reproductive and non-reproductive groups of either sex, suggesting t he absence of a physiologically well-defined suppression of reproduction in subordinate common mole-rats. (C) 2000 Academic Press.