AUTHOR=Goswami Chayon , Dezaki Katsuya , Wang Lei , Inui Akio , Seino Yutaka , Yada Toshihiko 

TITLE=Ninjin'yoeito Targets Distinct Ca2+ Channels to Activate Ghrelin-Responsive vs. Unresponsive NPY Neurons in the Arcuate Nucleus

JOURNAL=Frontiers in Nutrition

VOLUME=Volume 7 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2020.00104

DOI=10.3389/fnut.2020.00104

ISSN=2296-861X

ABSTRACT=Appetite loss or anorexia substantially deteriorates quality of life in various diseases, and stand upstream of frailty. The substance that counteracts appetite loss has long been awaited. Neuropeptide Y (NPY) in the hypothalamic arcuate nucleus (ARC) and ghrelin released from stomach are the most potent central and peripheral inducers of appetite, respectively. We previously reported that Ninjin’yoeito, a Japanese kampo medicine comprising twelve herbs, restores food intake and body weight in cisplatin-treated anorectic mice. Furthermore, Ninjin’yoeito increased cytosolic Ca2+ concentration ([Ca2+]i) in both ghrelin-responsive and unresponsive NPY neurons in ARC. However, significance of Ninjin’yoeito activation of two NPY neuron subpopulations remains unknown. This study sought to determine the occupancy of ghrelin-responsive vs. unresponsive NPY neurons in ARC and to explore the mechanisms underlying [Ca2+]i increases in these two NPY neuron subpopulations. Single neurons were isolated from ARC of mice, subjected to measurement of [Ca2+]i with fura-2, and subsequently immunostained for NPY. Among ARC NPY neurons, 58% responded but 42% did not respond to ghrelin with [Ca2+]i increases. In ghrelin-responsive ARC neurons, Ninjin’yoeito (10 µg/ml)-induced increases in [Ca2+]i were inhibited in Ca2+ free condition and by N-type Ca2+ channel blocker, -conotoxin, but not by L-type Ca2+ channel blocker, nitrendipine. In contrast, in ghrelin-unresponsive ARC neurons, Ninjin’yoeito-induced [Ca2+]i increases were inhibited in Ca2+-free condition and by nitrendipine but not -conotoxin. These results indicate that ghrelin-responsive and unresponsive NPY neurons are the major populations in ARC and activated by Ninjin’yoeito through distinct mechanisms, via N-type Ca2+ channels in ghrelin-responsive while L-type Ca2+ channels in ghrelin-unresponsive neurons. We suggest ARC N- and L-type Ca2+ channels as the potential targets for activating, respectively, ghrelin-responsive and unresponsive NPY neurons to treat anorexia.