NTS adenosine A2a receptors inhibit the cardiopulmonary chemoreflex control of regional sympathetic outputs via a GABAergic mechanism
| Autor: | Donal S. O'Leary, Zeljka Minic, Tadeusz J. Scislo |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
medicine.medical_specialty
Adenosine Sympathetic Nervous System Cardiovascular Neurohormonal Regulation Adenosine A2 Receptor Agonists Microinjections Receptor Adenosine A2A Physiology Morpholines Biguanides Adenosine A2A receptor Pharmacology Bicuculline GABA Antagonists Physiology (medical) Internal medicine Phenethylamines Reflex Solitary Nucleus medicine Animals Receptor Chemistry Solitary nucleus Solitary tract Heart Purinergic signalling Receptors GABA-A Adenosine A3 receptor Adenosine receptor Rats Serotonin Receptor Agonists Endocrinology Receptors GABA-B nervous system Cardiology and Cardiovascular Medicine medicine.drug |
| Zdroj: | American Journal of Physiology-Heart and Circulatory Physiology. 309:H185-H197 |
| ISSN: | 1522-1539 0363-6135 |
| Popis: | Adenosine is a powerful central neuromodulator acting via opposing A1 (inhibitor) and A2a (activator) receptors. However, in the nucleus of the solitary tract (NTS), both adenosine receptor subtypes attenuate cardiopulmonary chemoreflex (CCR) sympathoinhibition of renal, adrenal, and lumbar sympathetic nerve activity and attenuate reflex decreases in arterial pressure and heart rate. Adenosine A1 receptors inhibit glutamatergic transmission in the CCR pathway, whereas adenosine A2a receptors most likely facilitate release of an unknown inhibitory neurotransmitter, which, in turn, inhibits the CCR. We hypothesized that adenosine A2a receptors inhibit the CCR via facilitation of GABA release in the NTS. In urethane-chloralose-anesthetized rats ( n = 51), we compared regional sympathetic responses evoked by stimulation of the CCR with right atrial injections of the 5-HT3 receptor agonist phenylbiguanide (1–8 μg/kg) before and after selective stimulation of NTS adenosine A2a receptors [microinjections into the NTS of CGS-21680 (20 pmol/50 nl)] preceded by blockade of GABAA or GABAB receptors in the NTS [bicuculline (10 pmol/100 nl) or SCH-50911 (1 nmol/100 nl)]. Blockade of GABAA receptors virtually abolished adenosine A2a receptor-mediated inhibition of the CCR. GABAB receptors had much weaker but significant effects. These effects were similar for the different sympathetic outputs. We conclude that stimulation of NTS adenosine A2a receptors inhibits CCR-evoked hemodynamic and regional sympathetic reflex responses via a GABA-ergic mechanism. |
| Databáze: | OpenAIRE |
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