Electrophysiological characterization and MCH/orexin neuronal distribution in the lateral hypothalamus of naked mole-rats (Heterocephalus glaber)

The lateral hypothalamus (LH) controls various homeostatic processes, including sleep-wake cycles, energy balance and thermoregulation in many mammalian species. In the LH, melanin-concentrating hormone (MCH) and hypocretin/orexin (HO) containing neurons differentially regulate these processes. Naked mole-rats (NMR) ( Heterocephalus glaber ) are eusocial mammals with remarkable physiological peculiarities including extreme longevity without significant weight gain and absence of thermoregulation. Altered hypothalamic function could potentially underlie the unusual NMR phenotypes, but to date electrophysiological characterization of LH NMR neurons and expression of MCH and HO is missing. Here, we performed whole-cell recordings from LH neurons in acute NMR and mouse brain slices and found that NMR and mouse neuronal basic properties and activities were comparable. Additionally, we showed that both MCH-positive and HO-positive neuronal populations exist in the NMR hypothalamus and although the majority of MCH- and HO-positive neurons are located in the LH, as previously described in rodents, significant differences exist in MCH/HO distribution in other NMR hypothalamic areas. These results indicate that NMR LH neurons are comparable to mouse neurons with respect to their electrophysiological properties, but differences in the neuronal MCH and HO populations in hypothalamic regions exist and may contribute to the adaptive changes seen in NMR homeostatic processes.