Fig. 2. NPY/AgRP neurons and the orexigenic pathway. NPY/AgRP neurons have axon terminals that release GABA (an inhibitory neurotransmitter) to suppress the POMC neurons, PVH OXT neurons, and neurons within the L-PBN. PVH neurons that express PACAP/TRH have axon terminals that release glutamate (an excitatory neurotransmitter) to activate NPY/AgRP neurons. Functional connections between NPY/AgRP neurons and PVH neurons that express CRH/AVP have not been established (dotted lines). AgRP: agouti-related peptide, AVP: arginine vasopressin, CRH: corticotropin-releasing hormone, L-PBN: lateral parabrachial nucleus, NPY: neuropeptide Y, OXT: oxytocin, PACAP: pituitary adenylate cyclase-activating peptide, POMC: pro-opiomelanocortin, PVH: paraventricular nucleus of hypothalamus, TRH: thyrotropin-releasing hormone.