LEPTIN ACTIVATES NEURONS IN VENTROBASAL HYPOTHALAMUS AND BRAIN-STEM

Leptin is a circulating protein secreted by adipocytes which has profo und feeding, metabolic, and neuroendocrine effects. Leptin receptors h ave been localized to the hypothalamus, but the anatomic sites respons ible for mediating the effects of circulating leptin have not been dem onstrated. We report that systemic administration of leptin activates nuclear groups in the ventrobasal hypothalamus, including the ventrome dial, dorsomedial, and ventral premammillary hypothalamic nuclei. Lept in also activated the parvicellular subdivisions of the paraventricula r hypothalamic nucleus that; project to parasympathetic and sympatheti c preganglionic neurons. Finally, leptin administration activated the superior lateral parabrachial subnucleus, a nuclear group containing c holecystokinin neurons that project to the ventrobasal hypothalamus. T hese findings indicate that circulating leptin activates specific nucl ear groups in the hypothalamus and brainstem known to regulate complex physiological responses during times of substrate availability.