The Effects of Exogenous Midbrain Dopamine Antagonists on Vocalizations of a Teleost Fish, Porichthys notatus

Elizabeth HeislerHeisler
Advisor - J. Matthew Kittelberger

Studies investigating the neural mechanisms underlying context-dependent social-vocal behavior have used the plainfin midshipman fish Porichthys notatus as a model organism. Territorial male fish demonstrate different vocal behaviors depending on social context, producing antagonistic grunts to warn off predators and courtship hums to attract female mates. The architecture of the vocal-acoustic circuit involved in producing such social vocalizations has been well-characterized, and components of this circuit have been evolutionarily conserved in mammals. To achieve a greater understanding of how social-vocal behavior is shaped in humans, we are thus interested in ascertaining the neural mechanisms of the toadfish social-vocal circuit. While the neural structures contributing to vocal output of toadfish have been identified, it is unknown what modulates the behavioral shifts apparent when social context is altered. The catecholamine neurotransmitter dopamine has been shown to play a role in social behavior, reward, and motor control. Previous lab work has identified tyrosine hydroxylase, involved in synthesizing dopamine, throughout the plainfin midshipman vocal circuit, and injecting exogenous dopamine focally into the periaqueductal grey (PAG) of the midbrain significantly and reversibly inhibited vocal production. This study attempts to further elucidate the effects of dopamine and identify what receptors are involved in vocal social behavior by focally injecting dopamine antagonists into the periaqueductal grey, a midbrain vocal structure. SCH-23390, Sulpiride, and Fluphenazine were used to block D1-like receptors, D2-like receptors, and both D1-and D2-like receptors, respectively. Vocal output was elicited by stimulating the forebrain vocal areas and midbrain neuronal activity was recorded through an extracellular recording electrode on the occipital nerve. Changes in response probability, response duration, and response latency were investigated. Results show that Fluphenazine significantly blocks dopamine-induced inhibition of vocal response probability but does not completely restore it to control levels, while Sulpiride and SCH-23390 do not block the dopamine-induced inhibition. This suggests that both D1 and D2 dopamine receptors are involved in shifting among context-dependent social behaviors.