Local effects of substance P on respiratory regulation in the rat medulla oblongata.

摘要: The effect of substance P (SP) and the SP antagonist [D-Pro2,D-Trp7,9]-SP on basal ventilation was investigated in halothane-anesthetized rats. Microinjections (0.4-1.5 nmol) into ventrolateral medulla oblongata (VLM), (nuclei gigantocellularis, facialis, ambiguus, reticularis lateralis) or dorsomedial (DM, nucleus tractus solitarius) its ventral surroundings dose dependently increased tidal volume (VT) and/or minute ventilation. In sensitive areas, ventilatory stimulation initiated within minutes, peaked around 8-10 min, slowly returned to normal over 30-45 min after injection. VLM sites, increase VT generally accompanied by a decrease respiratory frequency (f), whereas DM, f parallel with VT. Furthermore, VLM, response patterns differed definite location A shortening inspiratory time observed ventromedial part, portion paragigantocellularis facialis. contrast, lengthening expiratory seen when injected applied more laterally along facialis near directly medullary surface. Application [D-Pro2, D-Trp7,9]SP before completely antagonized excitatory effects administered decreased hypoxic breathing but caused no change during hyperoxic conditions.