Acute Leptin Administration Increases Hypothalamic Expression of Prepro-orexin mRNA

The hypothalamus plays a central role in the integrated control of feeding. Thus, leptin has been shown to inhibit food intake apparently by inhibition of hypothalamic NPY. It has been proposed that the recently discovered orexigenic peptides named orexins could play a role analogous to that of NPY in the control of feeding. To test this hypothesis we determined the relative levels of hypothalamic prepro-orexin mRNA expression 2 h after a single dose (1 mg/kg, ip) of recombinant murine leptin in 48 h fasted mice by semiquantitative RT-PCR. We found an unexpected increase (34%; p < 0.04) of prepro-orexin mRNA which indicates that the neuronal pathways controlling feeding behaviour are more complex than initially thought and that the short-term regulation of neurotransmitters which control food intake may be different than medium- or long-term.