Effects of serotonin-1 and serotonin-2 receptor agonists on neuronal activity in the nucleus tractus solitarius

Abstract

Spontaneous neuronal activity in the solitary tract nucleus was recorded extracellularly in a brain slice preparation during bath-application of 5-HT 1 and 5-HT 2 receptor-selective agonists and antagonists. The 5-HT 1A/5-HT 1B agonist 5-carboxamidotryptamine depressed activity in 20 of 25 neurons studied. The remaining five neurons were unaffected. The 5-HT 1A/5-HT 1B antagonist pindolol prevented the 5-carboxamidotryptamine-induced changes, whereas the 5-HT 1A antagonist spiroxatrine and the 5-HT 2 antagonists ketanserin and mianserin were ineffective. Application of the 5-HT 1/5-HT 2 agonist α-methylserotonin depressed activity in 16 of 19 neurons, whereas the remaining three neurons were unresponsive. Pindolol blocked α-methylserotonin-induced changes of activity, but spiroxatrine, ketanserin and mianserin were ineffective. Finally, the 5-HT 2 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-HT 1 receptors in the nTS, presumably of the 5-HT 1B subclass, but cast further doubt on the contribution of 5-HT 2 and 5-HT 1A receptors to the actions of serotonin in the nucleus.