title: Dopamine microinjected into brainstem of awake rats affects baseline arterial pressure but not chemoreflex responses.
abstract: Dopamine (DA) is a neuromodulator in the brainstem involved with the generation and modulation of the autonomic and respiratory activities. Here we evaluated the effect of microinjection of DA intracisterna magna (icm) or into the caudal nucleus tractus solitarii (cNTS) on the baseline cardiovascular and respiratory parameters and on the cardiovascular and respiratory responses to chemoreflex activation in awake rats. Guide cannulas were implanted in cisterna magna or cNTS and femoral artery and vein were catheterized. Respiratory frequency (f(R)) was measured by whole-body plethysmography. Chemoreflex was activated with KCN (iv) before and after microinjection of DA icm or into the cNTS bilaterally while mean arterial pressure (MAP), heart rate (HR) and f(R) were recorded. Microinjection of DA icm (n=13), but not into the cNTS (n=8) produced a significant decrease in baseline MAP (-15+/-1 vs 1+/-1mmHg) and HR (-55+/-11 vs -11+/-17bpm) in relation to control (saline with ascorbic acid, n=9) but no significant changes in baseline f(R). Microinjection of DA icm or into the cNTS produced no significant changes in the pressor, bradycardic and tachypneic responses to chemoreflex activation. These data show that a) DA icm affects baseline cardiovascular regulation, but not baseline f(R) and autonomic and respiratory components of chemoreflex and b) DA into the cNTS does not affect either the autonomic activity to the cardiovascular system or the autonomic and respiratory responses of chemoreflex activation.
authors.affiliation: Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.
authors.forename: Waldyr M
authors.initials: WM
authors.lastname: Oliva
authors.forename: Erica M
authors.initials: EM
authors.lastname: Granjeiro
authors.forename: Leni G H
authors.initials: LG
authors.lastname: Bongamba
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Mendes
authors.forename: Benedito H
authors.initials: BH
authors.lastname: Machado
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001933:Brain Stem / Q000187:drug effects* / Q000378:metabolism; D002628:Chemoreceptor Cells / Q000187:drug effects*; D003243:Consciousness; D004298:Dopamine / Q000008:administration & dosage* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008845:Microinjections; D010993:Plethysmography, Whole Body; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D056152:Respiratory Rate / Q000187:drug effects / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D011190:Potassium Cyanide; D004298:Dopamine