Involvement of L-glutamate and ATP in the neurotransmission of the sympathoexcitatory component of the chemoreflex in the commissural nucleus tractus solitarii of awake rats and in the working heart-brainstem preparation

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dc.contributor.authorBraga, Valdir A.
dc.contributor.authorSoriano, Renato N.
dc.contributor.authorBraccialli, Alex L.
dc.contributor.authorde Paula, Patricia M.
dc.contributor.authorBonagamba, Leni G. H.
dc.contributor.authorPaton, Julian F. R.
dc.contributor.authorMachado, Benedito H.
dc.contributor.institutionUniversidade de São Paulo (USP)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.contributor.institutionUniv Bristol
dc.date.accessioned2014-05-20T13:45:39Z
dc.date.available2014-05-20T13:45:39Z
dc.date.issued2007-06-15
dc.description.abstractPeripheral chemoreflex activation with potassium cyanide (KCN) in awake rats or in the working heart-brainstem preparation (WHBP) produces: (a) a sympathoexcitatory/pressor response; (b) bradycardia; and (c) an increase in the frequency of breathing. Our main aim was to evaluate neurotransmitters involved in mediating the sympathoexcitatory component of the chemoreflex within the nucleus tractus solitarii (NTS). In previous studies in conscious rats, the reflex bradycardia, but not the pressor response, was reduced by antagonism of either ionotropic glutamate or purinergic P2 receptors within the NTS. In the present study we evaluated a possible dual role of both P2 and NMDA receptors in the NTS for processing the sympathoexcitatory component (pressor response) of the chemoreflex in awake rats as well as in the WHBP. Simultaneous blockade of ionotropic glutamate receptors and P2 receptors by sequential microinjections of kynurenic acid (KYN, 2 nmol (50 nl)(-1)) and pyridoxalphosphate-6-azophenyl-2',4'-disulphonate (PPADS, 0.25 nmol (50 nl)(-1)) into the commissural NTS in awake rats produced a significant reduction in both the pressor (+38 +/- 3 versus +8 +/- 3 mmHg) and bradycardic responses (-172 +/- 18 versus -16 +/- 13 beats min(-1); n = 13), but no significant changes in the tachypnoea measured using plethysmography (270 +/- 30 versus 240 +/- 21 cycles min(-1), n = 7) following chemoreflex activation in awake rats. Control microinjections of saline produced no significant changes in these reflex responses. In WHBP, microinjection of KYN (2 nmol (20 nl)(-1)) and PPADS (1.6 nmol (20 nl)(-1)) into the commissural NTS attenuated significantly both the increase in thoracic sympathetic activity (+52 +/- 2% versus +17 +/- 1%) and the bradycardic response (-151 +/- 17 versus -21 +/- 3 beats min(-1)) but produced no significant changes in the increase of the frequency of phrenic nerve discharge (+0.24 +/- 0.02+0.20 +/- 0.02 Hz). The data indicate that combined microinjections of PPADS and KYN into the commissural NTS in both awake rats and the WHBP are required to produce a significant reduction in the sympathoexcitatory response (pressor response) to peripheral chemoreflex activation. We conclude that glutamatergic and purinergic mechanisms are part of the complex neurotransmission system of the sympathoexcitatory component of the chemoreflex at the level of the commissural NTS.en
dc.description.affiliationUniv São Paulo, Dept Physiol, Sch Med, BR-14049900 Ribeirao Preto, Brazil
dc.description.affiliationSão Paulo State Univ, UNESP, Sch Dent, Dept Physiol & Pathol, BR-14801903 Araraquara, SP, Brazil
dc.description.affiliationUniv Bristol, Bristol Heart Inst, Dept Physiol, Sch Med Sci, Bristol BS8 2TD, Avon, England
dc.description.affiliationUnespSão Paulo State Univ, UNESP, Sch Dent, Dept Physiol & Pathol, BR-14801903 Araraquara, SP, Brazil
dc.format.extent1129-1145
dc.identifierhttp://dx.doi.org/10.1113/jphysiol.2007.129031
dc.identifier.citationJournal of Physiology-london. Oxford: Blackwell Publishing, v. 581, n. 3, p. 1129-1145, 2007.
dc.identifier.doi10.1113/jphysiol.2007.129031
dc.identifier.issn0022-3751
dc.identifier.urihttp://hdl.handle.net/11449/16070
dc.identifier.wosWOS:000247174700023
dc.language.isoeng
dc.publisherBlackwell Publishing
dc.relation.ispartofJournal of Physiology-london
dc.relation.ispartofjcr4.540
dc.relation.ispartofsjr2,051
dc.rights.accessRightsAcesso restrito
dc.sourceWeb of Science
dc.titleInvolvement of L-glutamate and ATP in the neurotransmission of the sympathoexcitatory component of the chemoreflex in the commissural nucleus tractus solitarii of awake rats and in the working heart-brainstem preparationen
dc.typeArtigo
dcterms.licensehttp://olabout.wiley.com/WileyCDA/Section/id-406071.html
dcterms.rightsHolderBlackwell Publishing
unesp.author.orcid0000-0001-5433-4493[4]
unesp.campusUniversidade Estadual Paulista (Unesp), Faculdade de Odontologia, Araraquarapt

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