S9-8 Wed Jan 6 16:00 – 16:30 Dopamine seasonally modulates adaptive sensitivity of the inner ear for reproductive communication in a vocal fish Perelmuter, JT*; Sisneros, JA; Forlano, PM; Cornell University; University of Washington; Brooklyn College email@example.com
The plainfin midshipman fish, Porichthys notatus, relies upon the production and reception of social acoustic signals to coordinate seasonal reproduction. As fish migrate to the intertidal zone in the summer, males establish rocky nests and produce nocturnal courtship calls. Females locate males for spawning based on this advertisement signal and, coincident with the breeding season, undergo a dramatic, hormonally regulated enhancement of peripheral auditory function which facilitates mate detection. Our recent work indicates that dopamine is an important contributor to this seasonal plasticity. Summer females in reproductive condition have reduced dopamine innervation of the saccule, the primary end organ for acoustic transduction in midshipman. Serial TEM analyses confirm reduced potential for dopaminergic release in the saccule during the breeding season. Dopaminergic boutons are smaller, fewer in number and less likely to directly contact hair cells in summer reproductive females as compared to winter, non-reproductive females. Exogenous dopamine and receptor-specific drugs applied to the saccule during sound-evoked recordings reveal that dopamine increases auditory thresholds via a D2-like receptor. Summer females express lower D2a levels than winter, non-reproductive females and D2a expression is negatively correlated with individual acoustic sensitivity, regardless of reproductive state. Altogether, these findings suggest that reduced dopaminergic innervation in the saccule, likely initiated by a seasonal change in circulating steroids, provides a release of inhibition, adaptively improving auditory sensitivity for mate localization. Adjusting the level of dopaminergic modulation in the peripheral auditory system may be a mechanism by which other vertebrate species modulate auditory sensitivity during critical periods of social interaction.