Nucleus tractus solitarius--gateway to neural circulatory control.

The neural regulation of the cardiovascular system has been the subject of active investigation for more than a century. Generally, the detailed infor­ mation available about peripheral mechanisms, both afferent and efferent, far exceeds what we know about the central nervous system (CNS) pro­ cessing, which gives rise to reflex responses (80). The current picture of the CNS contribution to cardiovascular regulation consists primarily of a loose network schematic including identified cell locations and connections involved in baroreflexes (Figure 1) and is the recent topic of several excellent, comprehensive reviews (80, 88, 132, 144). Much less is known about the functional properties by which these neurons communicate, how they are modulated, or the mechanisms responsible for various features of the reflex. Over the past ten years considerable research effort has focused on the initial neurons of the baroreceptor reflex, and it is here that work is most rapidly approaching issues of the cellular basis of function. Most cardio93