Emotional Vocalizations Alter Behaviors and Neurochemical Release into the Amygdala

The basolateral amygdala (BLA), a brain center of emotional expression, contributes to acoustic communication by first interpreting the meaning of social sounds in the context of the listener s internal state, then organizing the appropriate behavioral responses. We propose that modulatory neurochemicals such as acetylcholine (ACh) and dopamine (DA) provide internal-state signals to the BLA while an animal listens to social vocalizations. We tested this in a vocal playback experiment wherein we sampled fluids within the BLA and observed behavioral responses of male and female mice while presenting highly affective vocal sequences associated with either mating or restraint behaviors. In male mice, playback of restraint vocalizations increased ACh release and decreased DA release, while playback of mating sequences evoked the opposite neurochemical release patterns. In non-estrus female mice, the ACh and DA release patterns to mating playback were similar to males. Estrous females, however, showed increased ACh, associated with vigilance, as well as increased DA, associated with reward-seeking. Across these groups, increased ACh concentration was correlated with an increase in defensive behavior. These neurochemical release patterns and several behavioral responses depended on prior experience with the mating and restraint behaviors. Our results support a model in which ACh and DA provide contextual information to sound-analyzing BLA neurons that modulates their output to downstream brain regions responsible for appropriate behavioral outcomes.