Integration of systemic and visceral sensory information by medullary catecholaminergic systems during peripheral inflammation

Abstract

The nucleus of the solitary tract (nTS) is topographically organized with respect to the distribution of afferent sensory innervation and efferent projection patterns. Evidence suggests that the cells within the nTS, including medullary catecholaminergic (CA) neurons, are functionally diverse and that during peripheral inflammation they are recruited in a topographically organized manner that reflects their associations with afferent sensory systems. It is therefore feasible that topographically organized subdivisions of the nTS and the medullary CA neurons contained within them are differentially involved in signaling systemic (e.g., derived from blood-borne signals) versus visceral sensory information (e.g., derived from afferent sensory signals within the vagus nerve) during peripheral inflammation. The purpose of this review is to summarize (1) the topographic organization of afferent sensory input from vagal and systemic signaling pathways to the nTS in relation to medullary CA neurons and (2) the functional evidence to support the differential involvement of topographically organized subpopulations of CA and non-CA neurons in relaying signals of visceral versus systemic sensory information.