Meeting Abstract
Plasticity in sensory and motor circuitry underlies dramatic changes in seasonal reproductive behaviors across vertebrates. In female midshipman fish, seasonal, steroid-dependent plasticity in the auditory periphery functions to better encode frequencies of the male advertisement call. In addition, females are only motivated to respond and attend to advertisement calls when filled with mature eggs. Our recent investigations support brain-derived catecholamines, dopamine in particular, as important neuromodulators linking seasonal changes in audition with behavioral responsiveness to acoustic social signals in midshipman fish. Diencephalic dopaminergic (DA) neurons were found to directly innervate the inner ear and its cholinergic efferent nucleus in the hindbrain. Based on our prediction from seasonal changes in DA innervation of both these areas, we hypothesized an inhibitory effect of DA on the peripheral auditory system. Indeed, pharmacological studies combined with physiology demonstrate a robust inhibition by DA in the inner ear. These data suggest that an increase in auditory sensitivity during the reproductive period results from a release of DA inhibition. We also tested the hypothesis that females who exhibit a robust behavioral response to the male advertisement call would display elevated levels of neural activity within catecholaminergic neurons as measured by the immediate early gene product cFos. Three forebrain DA nuclei show increased cFos activation with time spent attending to a playback of the mate call. Neuroanatomical, physiological and behavioral evidence support diencephalic DA neurons as ideal candidate neuromodulators which function to integrate the detection and appropriate motor response to conspecific acoustic signals for successful reproduction.
