A rapid neuromodulatory role for steroid hormones in the control of reproductive behavior

The long-term transcriptional actions of steroids that shape neuronal morphology and the probability of behavioral expression are well established. More recently, attention has been focused on the role of rapid (minute-by-minute) steroid actions on neuronal mechanisms of reproductive behavior. In this review, we first consider the rapid actions of steroids on mating and copulatory behaviors in tetrapod vertebrates. Evidence for rapid effects of steroids is presented for chemoinvestigatory behavior (genital sniffing of females by male mice), lordosis (arched-back mating posture in female rats), copulatory mounting (male mice and male Japanese quail), reproductive clasping (pre-copulatory mounting in newts), and paced mating (copulation rate as determined by female rats). We then review recent studies in teleost fish that demonstrate the rapid actions of steroids on vocal patterning at two levels: (1) central pattern generators and (2) social behavior in natural environments. Thus, we propose that steroid-dependent modulation of central pattern generators can govern the overt expression of reproductive behaviors via rapid non-transcriptional mechanisms that are likely to be widespread among vertebrates.