title: Cardiovascular responses to microinjection of ATP into the nucleus tractus solitarii of awake rats.
abstract: Microinjection of increasing doses of ATP (0.31, 0.62, 1.25, and 2.5 nmol/50 nl) into the nucleus tractus solitarii (NTS) produced a dose-dependent pressor response. Prazosin abolished the pressor response and produced no change in the bradycardic response to ATP. Microinjection of pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (0.25 nmol/50 nl), a nonselective P2 receptor antagonist into the NTS, reduced the bradycardic response but had no effect on the pressor response to microinjection of ATP (1.25 nmol/50 nl) into the NTS. Microinjection of suramin (2 nmol/50 nl), another nonselective P2 receptor antagonist, had no effect on the pressor and bradycardic responses to microinjection of ATP (1.25 nmol/50 nl) into the NTS. Antagonism of A1 receptors of adenosine with 1,3-dipropyl-8-cyclopentylxanthine also produced no changes in the cardiovascular responses to microinjection of ATP into the NTS. The involvement of excitatory amino acid (EAA) receptors in the pressor and bradycardic responses to microinjection of ATP into the NTS was also evaluated. Microinjection of kynurenic acid, a nonselective EAA receptor antagonist (10 nmol/50 nl), into the NTS reduced the bradycardic response and had no effect on the pressor response to microinjection of ATP into the NTS. The data show that 1) microinjection of ATP into the NTS of awake rats produced pressor and bradycardic responses by independent mechanisms, 2) the activation of parasympathetic component may involve an interaction of P2 and EAA receptors in the NTS, and 3) the sympathoexcitatory response to microinjection of ATP into the NTS was not affected by the blockade of P2, A1, or EAA receptors.
authors.affiliation: Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.
authors.forename: Patrícia M
authors.initials: PM
authors.lastname: de Paula
authors.forename: Vagner R
authors.initials: VR
authors.lastname: Antunes
authors.forename: Leni G H
authors.initials: LG
authors.lastname: Bonagamba
authors.forename: Benedito H
authors.initials: BH
authors.lastname: Machado
mesh_terms: D058916:Adenosine A1 Receptor Antagonists; D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001286:Atropine Derivatives / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D007736:Kynurenic Acid / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D011224:Prazosin / Q000008:administration & dosage / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017552:Solitary Nucleus / Q000033:anatomy & histology / Q000502:physiology*; D013498:Suramin / Q000008:administration & dosage / Q000494:pharmacology; D014970:Xanthines / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D058916:Adenosine A1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D001286:Atropine Derivatives; D018691:Excitatory Amino Acid Antagonists; D058919:Purinergic P2 Receptor Antagonists; D014970:Xanthines; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; C006649:methylatropine; D000255:Adenosine Triphosphate; C051360:1,3-dipropyl-8-cyclopentylxanthine; D007736:Kynurenic Acid; D011224:Prazosin