Grant: CIHR Fellowship

Estrogens are implicated in an array of brain functions, many of which are critical for mental health. Thus, it important to understand how the effects of estrogen on physiology and behavior are coordinated in the central nervous system. Estrogen acts via genomic and non-genomic signaling mechanisms. Genomic signaling generally takes hours to days and its effects are long-lasting. Non-genomic signaling generally occurs within seconds to minutes and its effects are transient. Recent data suggest the balance between genomic and non-genomic estrogen signaling shifts seasonally. I propose to examine seasonal plasticity in estrogen signaling mechanisms in the brain that regulate aggression using a songbird model system. Male song sparrows display estrogen-dependent territorial aggression throughout the year. Aggression during a territorial intrusion is similar in spring and fall. But, aggression that occurs after an intrusion varies seasonally: spring aggression is persistent whereas fall aggression is transient. We hypothesize that this is associated with a seasonal shift in the role of genomic versus non-genomic estrogen signaling mechanisms. I propose three studies to test this hypothesis. First, the rapid effects of estrogen treatment on spring and fall aggression will be investigated. Second, the effects of a transient protein synthesis inhibitor on estrogen induced spring and fall aggression will be investigated. Third, differential centrifugation will be used to quantify the density of estrogen receptors mediating genomic (intracellular receptors) and non-genomic (membrane-associated receptors) signaling in the brains of spring and fall birds and the relationship between receptor density and aggression examined. Real-time PCR will also be used to compare estrogen-dependent gene expression in spring and fall birds. These studies will provide insight into the functional significance of genomic and non-genomic signaling in the brain.