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5‐HT2 receptor agonists modulate excitatory neurotransmission to cardiac vagal neurons within the nucleus ambiguus
Author(s) -
Dergacheva Olga,
Mendelowitz David
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a470-c
Subject(s) - ketanserin , excitatory postsynaptic potential , neurotransmission , 5 ht2 receptor , medicine , 5 ht receptor , agonist , serotonin , endocrinology , receptor , nucleus ambiguus , chemistry , neuroscience , biology , medulla oblongata , central nervous system
Previous studies have demonstrated an important role of serotonin (5‐HT), and particularly 5‐HT2 receptors, in parasympathetic cardiac control within the brainstem. This study examines whether 5‐HT2 receptors alter excitatory neurotransmission to cardiac vagal neurons (CVNs) within the nucleus ambiguus (NA). In an initial surgery, Sprague‐Dawley rats (postnatal days 2–7) were anesthetized and received a right thoractomy. The retrograde tracer rhodamine was injected onto the terminals of CVNs in the fat pads at the base of the heart to label CVNs. On the day of the experiments (2–4 days later), CVNs in the NA were identified in brainstem slices by the fluorescent tracer and studied using the whole‐cell patch‐clamp technique. To examine whether 5‐HT2 receptors modulate excitatory synaptic activity to CVNs, α‐methyl‐5HT (1 and 10 microM), a 5HT2 receptor agonist, and ketanserin (.1, 1 and 10 microM), a 5HT2A receptor antagonist, were focally applied to the patched CVNs. Application of α‐methyl‐5HT at a concentration of both 1 μM and 10 μM caused an increase in the frequency of EPSCs in CVNs. Ketanserin by itself had no effect. This work demonstrates activation of 5‐HT2 receptors facilitates excitatory synaptic activity to CVNs and likely mediates a centrally evoked decrease in heart rate when serotonin levels in the NA are increased.