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Department of Physiology, School of Medicine, Wayne State University, Detroit, Michigan 48201
Activation of
ATP P2x receptors in the subpostremal nucleus tractus
solitarii (NTS) via microinjection of
,
-methylene ATP (
,
-MeATP) elicits fast initial depressor and sympathoinhibitory responses that are followed by slow, long-lasting inhibitory effects. Activation of NTS adenosine A2a receptors via
microinjection of CGS-21680 elicits slow, long-lasting decreases in
arterial pressure and renal sympathetic nerve activity (RSNA) and an
increase in preganglionic adrenal sympathetic nerve activity
(pre-ASNA). Both P2x and A2a receptors may
operate via modulation of glutamate release from central neurons. We
investigated whether intact glutamatergic transmission is necessary to
mediate the responses to NTS P2x and A2a
receptor stimulation. The hemodynamic and neural (RSNA and pre-ASNA)
responses to microinjections of
,
-MeATP (25 pmol/50 nl) and
CGS-21680 (20 pmol/50 nl) were compared before and after pretreatment
with kynurenate sodium (KYN; 4.4 nmol/100 nl) in chloralose-urethan-anesthetized male Sprague-Dawley rats. KYN virtually
abolished the fast responses to
,
-MeATP and tended to enhance the
slow component of the neural responses. The depressor responses to
CGS-21680 were mostly preserved after pretreatment with KYN, although
the increase in pre-ASNA was reduced by one-half following the
glutamatergic blockade. We conclude that the fast responses to
stimulation of NTS P2x receptors are mediated via glutamatergic ionotropic mechanisms, whereas the slow responses to
stimulation of NTS P2x and A2a receptors are
mediated mostly via other neuromodulatory mechanisms.
nucleus tractus solitarii; purinergic receptors; ionotropic glutamatergic blockade; renal sympathetic nerve; adrenal sympathetic nerve
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