Role of the Carotid Sinus Nerve and of Dopamine in the Biochemical Response of Sympathetic Tissues to Long-Term Hypoxia
The sympathetic nervous system is known to react to hypoxia, but the response is not unitary and is dependent on hypoxic features (severe or moderate hypoxia, acute or chronic exposure), on the sympathetic nerve or tissue considered and on the state of animals (conscious or anesthetized) (Lee et al. 1987; Fitzgerald et al. 1990). Moreover, the mechanisms controlling the response of the sympathetic nervous system remain poorly understood and seem also highly dependent on tissues and on hypoxic conditions. Two components may be possible candidates for this regulation: one related to neural pathways coming from carotid bodies, and the other related to local dopaminergic events. In fact, previous data report that stimulation of carotid chemoreceptors by hypoxia elicits, or not, a sympathetic response indicating the involvement, or not, of a carotid chemoreceptor reflex (Matsumoto et al. 1987a, 1987b; Fukuda et al. 1989; Biesold et al. 1990; Fitzgerald and Deghani, 1990). As to concern dopamine (DA), it is able to induce an inhibitory electrophysiological and biochemical response of the postganglionic noradrenergic neurones, both in vitro and in vivo (Libet and Owman, 1974; Hanbauer, 1976; Ip et al., 1983; Brokaw et al., 1987). The role of DA located in the SIF cells of sympathetic ganglia may be evoked in this control.
KeywordsDioxide Dopamine Tyrosine Norepinephrine Epinephrine
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