Galanin injected into the hypothalamic PVN increases dopamine release and decreases acetylcholine in the nucleus accumbens system for behavior reinforcement

Galanin (GAL, 300 pmol), neuropeptide Y (NPY, 78 pmol) and saline were each injected ipsilaterally into the paraventricular nucleus (PVN) while extracellular dopamine (DA) and acetylcholine (ACh) were monitored in the nucleus accumbens (NAc). On a later day, injections were repeated in the same rats with food pellets available and intake measured. The result with GAL was a significant increase in DA (152% of baseline, n = 8) and a concomitant decrease in ACh (75% of baseline, n = 7). This was observed only in the animals that later proved to eat in response to GAL. Injections of NPY were without effect on DA and ACh whether they induced feeding or not. Saline injections had no effects. We conclude that when GAL in the PVN activates a circuit for eating food, it also activates circuitry that releases DA and inhibits ACh release in the NAc. This may be the link from a hypothalamic feeding mechanism to a NAc system for initiation and reinforcement of behavior. (Supported by USPHS grant NS 30697.).