Electrophysiology of the Appetite-Regulating Circuits of the Hypothalamus

This chapter considers the challenges that must be addressed in understanding gut-brain interactions in the regulation of feeding, and the contributions that electrophysiological studies have made so far, and might make in the future. It discusses authors' techniques for surgically exposing the ventral hypothalamus in anesthetized rats, and uses these to make extracellular recordings of single neurons in the supraoptic nucleus (SON), arcuate nucleus (ARC), and ventromedial nucleus of the hypothalamus (VMN) in vivo. This surgical approach enables us to introduce microelectrodes into specific hypothalamic regions under direct visual control to record the electrical activity of single neurons for many hours. The recent advent of new tools from optogenetics and pharmacogenetics approaches is now starting to make a major impact on our understanding of the appetite-regulating circuitry, and, in in vitro studies, these have been combined with electrophysiology to enable cells to be identified as well as manipulated.