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. 2013 Feb 26;4:15. doi: 10.3389/fendo.2013.00015

Figure 2.

Figure 2

Action of ghrelin in the brain. Ghrelin acts at different levels of the brain to stimulate food intake via hypothalamus and meso-cortico-limbic pathway. In the hypothalamus, ghrelin activates orexigenic neurons (AgRP/NPY), which inhibit anorexigenic neurons (POMC/CART) via GABA projections. They are connected to second order neurons like CRH and TRH neurons located in the PVN and/or the orexin neurons found in the LHA. POMC/CART neurons activate MCH neurons. Ghrelin acts also at different levels of meso-cortico-limbic pathway: LDTg, VTA, and Acc. Ghrelin acts directly on VTA to stimulate dopamine release in Acc. dopamine release is controlled by cholinergic LDTg neurons. Ghrelin could also act on NTS to stimulate the food intake via either vagal nerve or area postrema, see Figure 4. Acc, accumbens nucleus; ACh, acétylcholine; AgRP, agouti-related peptide; ARC, arcuate nucleus; CART, cocaine- and amphetamine-regulated transcript; CRH, corticotropin-releasing hormone; DA, dopamine; DYN, dynorphin; ENK, enkephalin; GABA, γ-aminobutyric acid; GHRH growth-hormone-releasing hormone; GLU, glutamate; LDTg, laterodorsal tegmental area; LHA, lateral hypothalamic area; MCH, melanin-concentrating hormone; NPY, neuropeptide Y; NTS, nucleus tractus solitarius; POMC, pro-opiomelanocortin; PVN, paraventricular nucleus; TRH, thyrotropin releasing hormone; VMH, ventromedial nucleus; VTA, ventral tegmental area.