Leptin regulated calcium channels of neuropeptide Y and proopiomelanocortin neurons by activation of different signal pathways

The fat-derived hormone leptin regulates food intake and body weight in part by modulating the activity of neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons in the hypothalamic arcuate nucleus (ARC). To investigate the electrophysiological activity of these neurons and their responses to leptin, we recorded whole-cell calcium currents on NPY and POMC neurons in the ARC of rats, which we identified by morphologic features and immunocytochemical identification at the end of recording. Leptin decreased the peak amplitude of high voltage-activated calcium currents (I-HVA) in the isolated neurons from ARC, which were subsequently shown to be immunoreactive for NPY. The inhibition was prevented by pretreatment with inhibitors of Janus kinase 2 (JAK2) and mitogen-activated protein kinases (MAPK). In contrast, leptin increased the amplitude of I-HVA in POMC-containing neurons. The stimulations of I-HVA were inhibited by blockers of JAK2 and phosphatidylino 3-kinase (PI3-k). Both of these effects were counteracted by the L-type calcium channel antagonist nifedipine, suggesting that L-type calcium channels were involved in the regulation induced by leptin. These data indicated that leptin exerted opposite effects on these two classes of neurons. Leptin directly inhibited I-HVA in NPY neurons via leptin receptor (LEPR) -JAK2-MAPK pathways, whereas evoked I-HVA in POMC neurons by LEPR-JAK2-PI3-k pathways. These neural pathways and intracellular signaling mechanisms may play key roles in regulating NPY and POMC neuron activity, anorectic action of leptin and, thereby, feeding. (C) 2008 Published by Elsevier Ltd on behalf of IBRO.