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 chemoreceptors (CC) in anesthetized vagotomized rats (sympathetic chemoreflex, SChR). Based on unit recording studies and experiments designed to impair synaptic transmission within selected lower brainstem nuclei or subregions, a model of the SChR is proposed with the essential features: i) key role of the nucleus of the solitary tract (NTS), rostral ventrolateral medulla (RVL) and ventrolateral pons (A5 area), ii) no role for caudal ventrolateral medulla (CVL), iii) modulatory role of dorsolateral pons and pre-Botzinger area, iv) dual control of bulbospinal presympathetic (preS) cells by CC inputs, one via the central respiratory network and the other through a direct excitatory pathway independent of the activity of this network, and v) independent medullary pathways for SChR and baroreflex until the preS neuronal stage in RVL.