Leptin modulation of peripheral controls of meal size.

Leptin reduces food intake through a specific effect on meal size. Investigations into how this within meal effect of leptin is mediated have demonstrated that leptin increases the ability of within meal inhibitory feedback signaling to limit intake and activate neurons within the nucleus of the solitary tract (NTS). Leptin's effects on neural activation can be demonstrated both as an increase in c-fos activation and as increase in electrophysiological activity in response to peripheral stimuli. Leptin can exert these effects through interactions at hypothalamic sites and activation of a descending pathway. NPY has opposite effect suggesting a role for reduced NPY signaling in the actions of leptin. Forebrain ventricular administration of a melanocortin agonist does not mimic the actions of leptin. As well as modulating within meal signaling through a descending pathway leptin, NPY and melanocortins could work directly at hindbrain integrative sites suggesting the possibility of distributed controls of meal size by anorexigenic and orexigenic signaling.