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Non‐NMDA receptors transmit cardiopulmonary C fibre input in nucleus tractus solitarii in rats.
Author(s) -
Wilson C G,
Zhang Z,
Bonham A C
Publication year - 1996
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1996.sp021726
Subject(s) - nucleus , nmda receptor , receptor , neuroscience , solitary nucleus , chemistry , medicine , biology
1. We sought first to determine whether neurones in caudomedial aspects of commissural nucleus tractus solitarii (NTS) received input from cardiopulmonary C fibre endings supplied by the pulmonary versus systemic circulation. We then examined the role of N‐methyl‐D‐aspartate (NMDA) and non‐NMDA receptors in transmitting cardiopulmonary C fibre input to such NTS neurones. 2. Extracellular NTS unit activity, phrenic nerve activity and arterial blood pressure were recorded in urethane‐anaesthetized rats. Unit responses to right atrial and left ventricular phenylbiguanide injections were compared in rats with arterial baroreceptors, carotid chemo‐receptors and subdiaphragmatic vagal inputs eliminated. Right atrial phenylbiguanide injections produced greater peak responses (27 +/‐ 11 impulses s‐1) than did left ventricular injections (11 +/‐ 3 impulses s‐1) (n = 9). 3. The non‐NMDA receptor agonist quisqualic acid (QUIS) and NMDA were ionophoresed onto NTS neurones that were synaptically activated by right atrial phenylbiguanide injection. Responses were compared before and during ionophoresis of the non‐NMDA receptor antagonist 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoylbenzo(f)quinoxaline (NBQX), the NMDA receptor antagonist DL‐2‐amino‐5‐phosphovaleric acid (AP5), or the broad spectrum antagonist kynurenic acid (KYN). 4. NBQX, which blocked QUIS‐but spared NMDA‐evoked responses, significantly attenuated synaptic activation by 65% (n = 9). AP5, which blocked NMDA‐ but spared QUIS‐evoked responses, did not significantly diminish synaptic activation (11%; n = 7). KYN, which blocked QUIS‐ and NMDA‐evoked responses, decreased synaptic activation by 70% (n = 9). 5. The results suggest that input from cardiopulmonary C fibre endings, primarily supplied by the pulmonary circulation, is transmitted to this commissural NTS region largely via non‐NMDA receptors.