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Department of Physiology, Wayne State University, School of Medicine, Detroit, Michigan 48201
Activation of adenosine
A2a and ATP
P2x purinoceptors in the
subpostremal nucleus tractus solitarii (NTS) via microinjection of the
selective agonists CGS-21680 and
,
-methylene ATP (
,
-MeATP), respectively, elicits large dose-dependent decreases in arterial pressure and heart rate, differential regional vasodilation, and differential inhibition of regional sympathetic outputs. With marked
hypotensive hemorrhage, preganglionic adrenal sympathetic nerve
activity (pre-ASNA) increases, whereas renal (RSNA) and postganglionic
adrenal sympathetic nerve activity (post-ASNA) decrease. In this
setting, adenosine levels in the brain stem increase. Therefore, we
investigated whether stimulation of specific purinoceptors in the NTS
may evoke differential sympathetic responses. RSNA was recorded
simultaneously with pre-ASNA or post-ASNA in chloralose-urethan-anesthetized male Sprague-Dawley rats.
CGS-21680 (2 and 20 pmol in 50 nl) inhibited RSNA and post-ASNA,
whereas pre-ASNA increased markedly.
,
-MeATP (25 and 100 pmol in
50 nl) inhibited all sympathetic outputs. Sinoaortic denervation plus
vagotomy markedly prolonged the responses to
P2x-purinoceptor stimulation.
Glutamate (100 pmol in 50 nl) caused differential inhibition of all
sympathetic outputs similar to that evoked by
,
-MeATP. We
conclude that NTS A2a-purinoceptor
activation evokes differential sympathetic responses similar to those
observed during hemorrhage, whereas
P2x-purinoceptor and
glutamate-receptor activation evokes differential inhibition of
sympathetic outputs similar to arterial baroreflex responses.
adrenal sympathetic nerve; renal sympathetic nerve; purinergic receptor subtypes; nucleus of the solitary tract; cardiovascular control
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