Orexin-A and orexin-B are differently localized in the pars nervosa and pars distalis of the white-spotted conger and Japanese eel pituitaries

The distribution of orexin-A and orexin-B immunoreactivity was examined in the pituitaries of the white-spotted conger (Conger myriaster) and the Japanese eel (Anguilla japonica) using immunohistochemical techniques. Orexin-A-immunoreactive puncta were dispersed in the pars nervosa of the neurointermediate lobe, and a part of these puncta were immuno-positive for galanin. In contrast, orexin-B immunoreactive cells were observed in the proximal part of the pars distalis, and these cells were immuno-positive for luteinizing hormone. Considering the present results and previous findings, orexin-A and orexin-B may modulate the secretion of α-melanocyte-stimulating hormone and growth hormone, respectively, and participate in the regulation of energy homeostasis.