Endocrine Abstracts

During the last two decades attention has been focused on the role of different neuropeptides in hypothalamic control of feeding behavior. Se-veral hypothalamic peptides that participate in the control of ingestive behavior are produced in neuronal cell bodies of the arcuate nucleus and/or the lateral hypothalamic area. Apart from producing orexigenic or anorexigenic compounds of peptidergic nature, it has recently become apparent that these neurons also produce several classical neurotrans-mitters. The role of classical transmitters in regulating energy ba-lance has received less attention in comparison to neuropeptides. The arcuate nucleus-median eminence area, a region with a weak blood-brain barrier (BBB), contains at least two neuronal cell populations that exert oppo-sing actions on energy balance. The majority of the neurons located in the ventromedial aspect of the arcuate nucleus, which pro-duce the or-exigenic peptides neuropeptide Y (NPY) and agouti-related peptide (AGRP), in addition contain the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD) and the vesicular GABA transporter (VGAT), thereby supporting their GABAergic nature. Subpopulations of anorexi-genic neurons producing proopiomelanocortin (POMC)- and cocaine- and amphetamine-regulated transcript (CART), located in the ventro-lateral division of the arcuate nucleus have recently been reported to contain the vesicular acetylcholine (ACh) transporter (VAChT) and cho-line acetyltransferase (ChAT), markers for cholinergic neurons, or the vesicular glutamate transporter 2 (VGLUT2), a marker for glutamatergic neurons. In addition, two new neuropeptides in have been identified in arcuate POMC neurons. In the lateral hypothalamic area, hypocretin-/orexin neurons express VGLUT1 or VGLUT2, but not GAD, whereas some melanin-concentrating hormone (MCH) cells contain GAD. These observations support the view that ACh, GABA and glutamate, relatively neglected feeding transmitters, are present in neurons that regulate body weight and consequently may represent important orexigenic-/anorexigenic mediators that convey information from the hypo-thalamus to other brain regions that participate in regulation of energy balance.