Dopamine injections to the midbrain periaqueductal gray inhibit vocal-motor production in a teleost fish.

Across vertebrates, the midbrain periaqueductal gray (PAG) plays a critical role in social and vocal behavior. Dopaminergic neurotransmission also modulates these behaviors, and dopaminergic innervation of the PAG has been well documented. Nonetheless, the potential role of dopamine in shaping vocal production at the level of the PAG is not well understood. Here, we tested the hypothesis that dopamine modulates vocal production in the PAG, using a well-characterized vertebrate model system for the study of vocal communication, the plainfin midshipman fish, Porichthys notatus. We found that focal dopamine injections to the midshipman PAG rapidly and reversibly inhibited vocal production triggered by stimulation of known vocal-motor structures in the preoptic area / anterior hypothalamus. While dopamine inhibited vocal-motor output, it did not alter behaviorally-relevant parameters of this output, such as vocalization duration and frequency. Dopamine-induced inhibition of vocal production was prevented by the combined blockade of D1- and D2-like receptors but was unaffected by isolated blockade of either D1-receptors or D2-receptors. Our results suggest dopamine neuromodulation in the midshipman PAG may inhibit natural vocal behavior, in courtship and/or agonistic social contexts.