Brainstem-hypothalamic neuropeptides and the regulation of feeding

The brainstem contains all the necessary circuitry that is required to control the basic mechanisms of feeding and to regulate the size of individual meals. This is achieved through reciprocal connections with the whole length of the gastrointestinal tract. Any meal is initiated by feed-forward sensory information and is terminated by feedback information. To modulate eating with respect to other facets of energy homeostasis, the brainstem detects neuronal and hormonal signals from the gut and other organs, and integrates this information by communication with higher brain centers. This chapter is focused to assess the role of neuropeptides with particular reference to the dorsal vagal complex. The term neuropeptide is treated in its widest context to include peptide transmitters and peptide hormones. Some neuropeptides that are intrinsic to the brainstem itself may have as important roles in energy homeostasis as their hypothalamic counterparts. The modulation of brainstem function by descending peptidergic pathways from higher brain centers suggests that the brainstem is a target for pharmaceutical intervention. There are peptidergic inputs from the periphery either carried neuronally or humorally. These signals are integrated by the nucleus of the tractus solitarius (NTS) and projected back to the periphery or to other brain centers. Descending peptidergic pathways further modulate the NTS. The importance of peptidergic neurons that are intrinsic to the NTS is being appreciated and they may yet prove to be as crucial in regulating appetite and body weight as some of their hypothalamic counterparts. © 2007 Elsevier Inc. All rights reserved.