Leptin transiently antagonizes ghrelin and long-lastingly orexin in regulation of Ca2+ signaling in neuropeptide Y neurons of the arcuate nucleus

Figure 1 Ghrelin- and orexin-induced [Ca²⁺]_i increases were suppressed by leptin in a transient or long-lasting manner in NPY neurons. A-D: Ghrelin and orexin-A at 10^-10 mol/L increased [Ca²⁺]_i in single neurons isolated from the ARC, and these [Ca²⁺]_i increases were suppressed by administration of leptin at 10^-12 mol/L (A, C) and 10^-14 mol/L (D). Following [Ca²⁺]_i measurements, the neurons in (A) and (C) were proved to contain NPY by immunocytochemistry using anti-NPY antibody (A, C; right panels). The bars indicate 10 μm. E: Leptin inhibited ghrelin-induced [Ca²⁺]_i increases in a greater number of neurons in 2-7 min after administration than in 10-15 min. In contrast, leptin inhibited orexin-A-induced [Ca²⁺]_i increases in the majority of neurons in 2-7 min and 10-15 min after administration. The numbers above the bars indicate the number of neurons inhibited by leptin over that responded to ghrelin or orexin-A. F: The number of neurons whose [Ca²⁺]_i responses to ghrelin or orexin-A were suppressed by leptin in either a transient or long-lasting manner is expressed by percentage. The numbers above the points indicate the number of neurons inhibited by leptin in the specified manner over that responded to ghrelin or orexin-A.