Evidence that female endocrine state influences catecholamine responses to male courtship song in European starlings

Abstract

Little is known about the neural control of female responses to male courtship. Female European starlings in breeding condition with high concentrations of estrogen select mates based on variation in song and approach nest boxes broadcasting male song. In contrast, outside of the breeding season (when estrogen is low) females do not display the same response to male song. The catecholamines dopamine and norepinephrine regulate behaviors important for mate choice such as arousal, attention, sexual motivation, and goal-directed approach responses, suggesting a role for catecholamines in female responses to male song. In the present study, treating females with a dopamine agonist inhibited, whereas an antagonist stimulated female interest in nest boxes broadcasting male song. In a second study immunocytochemistry was used to examine the distribution of the phosphorylated (i.e., active) form of tyrosine hydroxylase (pTH), the rate-limiting enzyme for catecholamine synthesis. Exposure to male song in breeding condition females reduced pTH density in brain regions involved in social behavior (lateral septum, ventromedial nucleus of the hypothalamus) and a region involved in visual processing (nucleus of Edinger-Westphal) but not song control regions. Opposite patterns of pTH labeling densities were observed in the same regions in response to song in non-breeding condition females. pTH in the ventral tegmental area was also affected by song and female endocrine condition. Overall, the present data support an inhibitory role for dopamine in female responses to courtship and suggest that endocrine state and catecholamines interact to regulate this behavior.