Inhibition of rat nucleus tractus solitarius neurones by activation of 5-HT2C receptors.

In vivo, nucleus tractus solitarius (NTS) neurones receiving monosynaptic vagal input and inactive intermediate neurones were inhibited by both DOI and a selective 5-HT2C receptor agonist, MK-212. Cells receiving a more polysynaptic input were excited by DOI and although MK-212 also excited a few of these cells, the majority of cells in these groups were unaffected by MK-212. The inhibitory, but not the excitatory actions of both MK-212 and DOI were prevented by a selective 5-HT2C receptor antagonist, RS-102221. In contrast, most dorsal vagal preganglionic neurones were unaffected by application of either DOI or MK-212, the few remaining cells being excited by both agonists. These data demonstrate that DOI-evoked inhibition of NTS cells activated by vagal afferent input and DOI-evoked excitation of vagal preganglionic neurones is mediated by 5-HT2C receptors.