EFFECT OF PROLACTIN ON THE ATTRACTIVENESS OF MALE ODORS TO FEMALES INMEADOW VOLES - INDEPENDENT AND ADDITIVE EFFECTS WITH TESTOSTERONE

This study investigated the roles of testosterone and prolactin in sea sonal changes in the attractiveness of odors of male meadow voles to l ong-photoperiod females. Prolactin was reduced in long-photoperiod mal es by treatment with bromocryptine (Experiment 1) and increased in sho rt-photoperiod males by replacement with ovine prolactin (Experiment 2 ). Testosterone was manipulated by castration and testosterone replace ment. During long photoperiods, the attractiveness of the odor produce d by male meadow voles depends on the circulating titers of both prola ctin and testosterone. Males with high titers of both hormones produce d scents that were highly attractive to females; those with low titers of both hormones produced unattractive scents. When the concentration of one hormone was high and the other low, long-photoperiod males pro duced scents of intermediate attractiveness. During short photoperiods , the attractiveness of the male's scents depended strictly on his pro lactin titers. Males with high prolactin titers produced attractive sc ents, and males with low prolactin titers produced unattractive scents , regardless of their prolactin concentrations. Thus, high titers of b oth testosterone and prolactin are needed to produce attractive scents in males exposed to long photoperiods, whereas high prolactin titers are sufficient in short-photoperiod males. (C) 1997 Academic Press.