Oxygen Sensing by the Brainstem in Respiratory Control

State University of New York at Stony Brook Stony Brook, New York, U.S.A. 

Both depressant and excitatory effects of hypoxia have been assigned to the loci primarily in the CNS and for each, both direct and indirect mechanisms have been proposed. In this review, direct mechanisms refer to a proposed chemoreceptor-like function in specific loci in the CNS. Indirect mechanisms refer to a variety of phenomena such as disinhibition of diencephalic facilitation of respiratory activity by the depressant effect of hypoxia on the cortex or the increase of levels of both excitatory and inhibitory neuromodulators in the nucleus tractus solitarius (NTS) associated with stimulation of the peripheral chemoreceptors. 

It is the thesis of this review that for the most part, both the excitatory and depressant ventilatory effects of CNS hypoxia are specific adaptive processes, phylogeneticaUy and perhaps ontologicaUy conserved, rather than nonspecific events brought about by insufficient substrate availability for neuronal energy metabolism. 

Marcel Dekker, Inc. 270 Madison Avenue, New York, New Yoik 10016 

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