WORKING MODEL OF THE SYMPATHETIC CHEMOREFLEX IN RATS

This review examines the neural network responsible for activation of the sympathetic vasomotor system during stimulation of carotid chemore ceptors (CC) in anesthetized vagotomized rats (sympathetic chemoreflex , SChR). Based on unit recording studies and experiments designed to i mpair synaptic transmission within selected lower brainstem nuclei or subregions, a model of the SChR is proposed with the essential feature s: i) key role of the nucleus of the solitary tract (NTS), rostral ven trolateral medulla (RVL) and ventrolateral pens (A5 area), ii) no role for caudal ventrolateral medulla (CVL), iii) modulatory role of dorso lateral pens and pre-Botzinger area, iv) dual control of bulbospinal p resympathetic (preS) cells by CC inputs, one via the central respirato ry network and the other through a direct excitatory pathway independe nt of the activity of this network, and v) independent medullary pathw ays for SChR and baroreflex until the preS neuronal stage in RVL.