Meeting Abstract
Although dopamine has been identified as an efferent neuromodulator in the rodent peripheral auditory system, its functional role in audition related to adaptive behaviors is unknown, and similar investigations have not been conducted in anamniotes. Our lab has identified dopaminergic innervation in the inner ear of the plainfin midshipman (Porichthys notatus), a marine teleost that utilizes vocal signals for seasonal reproduction. Females undergo a hormone-dependent enhancement of hearing during the summer reproductive season that coincides with a reduction in the dopaminergic input to the ear, suggesting that dopamine has an inhibitory effect on inner ear physiology. We therefore tested the hypothesis that dopamine would reduce the auditory sensitivity of the saccule, the main organ of hearing in midshipman. Auditory evoked potentials of saccular hair cells were recorded in the presence of dopamine and receptor agonists. Dopamine and a D2 receptor agonist (quinpirole) inhibited auditory evoked responses by raising thresholds (i.e., decreasing auditory sensitivity), however a D1 receptor agonist (SKF-38393) had no effect. Furthermore, a D2 receptor antagonist (sulpiride) blocked the inhibitory action of dopamine. Our results suggest that seasonal changes in dopaminergic tone may be an important mechanism that contributes to the seasonal plasticity of auditory sensitivity reported for the midshipman. This is the first demonstration of dopaminergic modulation of inner-ear auditory sensitivity in an anamniote and raises the possibility that dopamine may be a conserved modulator of peripheral auditory processing across vertebrates.
