Effects of serotonin-1 and serotonin-2 receptor agonists on neuronal activity in the nucleus tractus solitarius.
Spontaneous neuronal activity in the solitary tract nucleus was recorded extracellularly in a brain slice preparation during bath-application of 5-HT1 and 5-HT2 receptor-selective agonists and antagonists. The 5-HT1A/5-HT1B agonist 5-carboxamidotryptamine depressed activity in 20 of 25 neurons studied. The remaining five neurons were unaffected. The 5-HT1A/5-HT1B antagonist pindolol prevented the 5-carboxamidotryptamine-induced changes, whereas the 5-HT1A antagonist spiroxatrine and the 5-HT2 antagonists ketanserin and mianserin were ineffective. Application of the 5-HT1/5-HT2 agonist alpha-methylserotonin depressed activity in 16 of 19 neurons, whereas the remaining three neurons were unresponsive. Pindolol blocked alpha-methylserotonin-induced changes of activity, but spiroxatrine, ketanserin and mianserin were ineffective. Finally, the 5-HT2 agonist DOI was applied to seven neurons. Six were unresponsive to DOI, and one responded with a depression of activity. These data provide electrophysiological evidence for the presence of 5-HT1 receptors in the nTS, presumably of the 5-HT1B subclass, but cast further doubt on the contribution of 5-HT2 and 5-HT1A receptors to the actions of serotonin in the nucleus.
Feldman
P D
PD
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Medical Center, New Orleans 70112-1393, USA.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects*; D010869:Pindolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D017552:Solitary Nucleus / Q000187:drug effects*
D017366:Serotonin Receptor Agonists; D007650:Ketanserin; D010869:Pindolol