Topochemistry of Internuclear and Intranuclear Interneurons of the Vasomotor Area in the Medulla Oblongata of Hypertensive Rats

Abstract

Immunohistochemical examination with the antiserum against neuronal NO synthase and cystathionine β-synthase was used to study the following two pools of interneurons in Wistar rats at various periods after the development of renovascular hypertension: intranuclear interneurons (lying in the projection of the solitary nucleus, reticular gigantocellular nucleus, and parvocellular nucleus) and 2 groups of internuclear interneurons (small interneurons, area 50-300 μ²; and large interneurons, area above 350 μ²). Intranuclear and internuclear interneurons probably play a role in the central mechanisms of hemodynamics regulation. These interneurons differ by not only in topochemical parameters, but also functional properties (different resistances to BP changes). Intranuclear interneurons are characterized by high sensitivity of the gas transmitter systems to a continuous increase in BP, which results in remodeling and dysfunction of the bulbar part of the cardiovascular center. Large internuclear interneurons demonstrate a strong reaction to BP rise, which confirms their involvement into hemodynamics regulation. By contrast, small internuclear interneurons retain their characteristics in arterial hypertension and probably perform an integrative function.