Noradrenergic inhibitory modulation in the caudal commissural NTS of the pressor response to chemoreflex activation in awake rats.
In the present study we evaluated the possible modulatory role of noradrenaline on the neurotransmission of the peripheral chemoreflex afferents in the caudal commissural NTS of awake rats. To reach this goal we performed a dose-response curve to microinjection of increasing dose of noradrenaline into the caudal commissural NTS of awake rats and then the threshold dose, which produces minor changes in the baseline mean arterial pressure, was selected to be used in the chemoreflex experiment. The peripheral chemoreflex was activated with KCN before and after bilateral microinjections of noradrenaline (5 nMol/50 nL, threshold dose) into the NTS. The data show that microinjection of noradrenaline into the caudal NTS produced a significant reduction in the pressor response to the chemoreflex 30 s after the injection when compared to the control response (30+/-6 vs. 49+/-3 mm Hg) but no significant changes in the bradycardic response. The data indicate that noradrenaline in the caudal commissural NTS of awake rats may play an important inhibitory neuromodulatory role on the processing of the pressor/sympathoexcitatory component of the chemoreflex.
Silva de Oliveira
Luciana C
LC
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes, 3900, 14049-900, Ribeirão Preto, SP, Brazil.
Bonagamba
Leni G H
LG
Machado
Benedito H
BH
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D001919:Bradycardia / Q000139:chemically induced; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008845:Microinjections; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism* / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000378:metabolism / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D017833:Visceral Afferents / Q000187:drug effects / Q000502:physiology; D014851:Wakefulness / Q000502:physiology
D014662:Vasoconstrictor Agents; D011190:Potassium Cyanide; D009638:Norepinephrine