Dopamine and ACH involvement in plastic learning by hypothalamic neurons in rats

Unit activity in the rat lateral hypothalamus (LHA) was recorded during discrimination learning of cue tone stimuli (CTS). CTS⁺ predicted reward (glucose or intracranial self-stimulation); CTS^- predicted aversion (electric shock or tail pinch); and all behavior responses were by the same act, licking. Roles of the LHA dopaminergic and cholinergic systems in CTS learning were investigated by electrophoretic application of dopamine (DA) and acetylcholine (ACh), and their antagonists. The CTS⁺, the predicted reward and DA, all had similar effects (inhibition) on many LHA neurons; and these were all opposite to the effects (excitation) of CTS^-, the predicted aversion, and ACh. Neural responses to CTS⁺ were blocked by spiperone, and responses to CTS^- were blocked by atropine. Sensitivity of LHA neurons to DA was reduced by extinction of CTS⁺ learning for reward, and sensitivity to ACh was reduced by CTS^- learning for aversion. The data suggest that afferent DA and ACh inputs to LHA neurons are essential for plastic CTS⁺ and CTS^- learning.