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Involvement of ATP and L‐glutamate in the neurotransmission of the sympathoexcitatory component of the chemoreflex in the commissural NTS in the working heart‐brainstem preparation (WHBP) of rat.
Author(s) -
Braga Valdir A,
Soriano Renato N,
Paton Julian FR,
Machado Benedito H
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a467
Subject(s) - ppads , ionotropic effect , neurotransmission , glutamatergic , glutamate receptor , purinergic receptor , chemistry , kynurenic acid , neurotransmitter , medicine , neuroscience , endocrinology , receptor , biology , biochemistry
Peripheral chemoreflex activation with potassium cyanide (KCN) in the WHBP produces sympathoexcitation, bradycardia and increase in the frequency of phrenic nerve activity (PNA). The aim was to evaluate the neurotransmitter(s) involved in mediating the sympathoexcitatory component of the chemoreflex within the caudal commissural NTS (cNTS). Based on our previous data, we hypothesized dual transmission. Simultaneous antagonism of ionotropic glutamate receptors and P2 receptors by sequential microinjections of kynurenic acid (KYN, 2 nmol/20 nL) and pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulfonate (PPADS, 1.6 nmol/20 nL) into the cNTS (n=9) significantly attenuated both the increase in thoracic sympathetic activity (+52±2 vs +17±1 %; P < 0.001 ) and the bradycardic response (−151±17 vs −21±3 bpm ; P < 0.001 ). In contrast, there was no significant changes in the chemoreflex evoked increase PNA frequency. We conclude that both glutamatergic and purinergic mechanisms are part of the complex neurotransmission system of the sympathoexcitatory component of the chemoreflex within the cNTS. The absence of effect on the evoked PNA response suggests that this component of the chemoreflex is not dependent on a combination of ionotropic glutamate and P2 receptors in the cNTS. Supported by FAPESP and CNPq (Brazil) and BHF (UK).