Meeting Abstract
Vocal signals convey information about an individual’s motivational and social status. As circumstances change, individuals adjust vocal behavior accordingly. It is common for individuals that gain a territory to immediately increase the production of agonistic or courtship vocalizations. These behavioral changes are associated with rapid increases in steroid hormones, yet the mechanisms by which steroids modify motivation neural systems to adjust vocal production are not well known. I will present studies addressing this topic in male European starlings, Sturnus vulgaris. In spring, T concentrations rise and male starlings initiate breeding activities. However, not all males display courtship behavior at this time. Among males with elevated T, only males that obtain a nesting site (or nest box) produce high rates of sexually-motivated courtship song. These behavioral changes can occur rapidly (within minutes to hours after nest box acquisition) and are accompanied by an increase in circulating T and increased densities of androgen receptors in the medial preoptic nucleus (POM, a region in which T promotes male sexual motivation). A mechanism by which T in POM may rapidly modify motivational state (and status-appropriate song) is through its interactions with opioid neuropeptides. High singing males with nest boxes have low densities of mu opioid receptors and enkephalin opioids in POM compared to low singing males without nest boxes. Pharmacology studies further indicate that a low level of opioid receptor stimulation in POM is needed to facilitate sexually-motivated song but higher levels of stimulation inhibit singing behavior. We present evidence indicating that relatively rapid increases in T may fine-tune opioid-related gene expression in POM to promote status-appropriate singing behavior.
