In vivo modulation of nucleus tractus solitarius (NTS) neurones by activation of 5-hydroxytryptamine(2) receptors in rats.
In in vivo experiments, 5-hydroxytryptamine (5-HT) and (+/-)-2,5-dimethoxy-4-iodoamphetamine HCl (DOI), a 5-HT(2) receptor agonist, were applied by ionophoresis to rat nucleus tractus solitarius (NTS) neurones identified by their vagal and cardiopulmonary afferent inputs to test whether the response of NTS cells to 5-HT(2) receptor activation was related to whether they received mono- or polysynaptic vagal inputs and their presumed function as defined by their afferent input. Cells were classified on the basis of the variability of the latency of the vagal-evoked spikes: this varied by less than 3 ms for Group 1, from 3 to 5 ms for Group 2, and more than 5 ms for Group 3. Both 5-HT and DOI inhibited most Group 1 cells (16/18) and inactive (without ongoing activity) cells (8/13) in Group 2. Cells inhibited by DOI were also inhibited by cardiopulmonary afferent stimulation, evoked by atrial phenylbiguanide administration. By contrast, application of 5-HT and DOI excited the majority of Group 3 cells (14/19) and Group 2 with ongoing activity (7/9). Cells excited by DOI were also activated by cardiopulmonary stimulation. Both actions of DOI were reversed by application of ketanserin (n=15). In conclusion, these data demonstrate that activation of 5-HT(2) receptors in the NTS produces different effects dependent on whether the neurones received mono- or polysynaptic vagal input and their response to cardiopulmonary afferent stimulation.
Sévoz-Couche
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Department of Physiology, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, UK. csevoz@rfhsm.ac.uk
Wang
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Ramage
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Spyer
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Jordan
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D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000662:Amphetamines / Q000494:pharmacology*; D000818:Animals; D016166:Free Radical Scavengers / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D017552:Solitary Nucleus / Q000187:drug effects* / Q000502:physiology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology
D000662:Amphetamines; D016166:Free Radical Scavengers; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine