Involvement of orexin A and melanin concentrating hormone neurons of the lateral hypothalamic area in the food intake response to reduced glucose availability

The purpose of the present study was to elucidate the involvement of melanin concentrating hormone (MCH) and orexin A neurons at the lateral hypothalamic area (LHA) in the regulation of food intake stimulated by reduced glucose availability. In the present study, we examined the food intake response and c‐Fos expression in the MCH and orexin A neurons after 2‐deoxy‐D‐glucose (2DG)‐induced glucoprivation or systemic insulin‐induced hypoglycemia. Nine‐week‐old male rats were injected with either 2‐deoxy‐D‐glucose (2DG; 400 mg/kg; i.v.) or insulin (5 units/kg; s.c.), and food and water intakes were measured. Two days after the behavioral test, we examined c‐Fos expression in the MCH and orexin A neurons in the LHA immunohistochemically after 2DG or insulin administration. Both MCH and orexin A neurons were located in the LHA, but these peptides were distinctly localized in the separate neurons. Both 2DG and insulin administrations increased food intake compared with saline administration, and induced c‐Fos expression in the orexin A neurons, but did not induce c‐Fos expression in the MCH neurons of the LHA. These data indicate that orexin A neurons play a role but MCH neurons are not involved in the food intake response to reduced glucose availability.