Article date: December 2000
By: Caroline Sévoz‐Couche, K Michael Spyer, David Jordan in Volume 131, Issue 7, pages 1445-1453
In in vivo experiments, DOI (a 5‐HT2 receptor agonist), MK‐212 (a 5‐HT2C receptor agonist), and BW‐723C86 (a 5‐HT2B receptor agonist) were applied by ionophoresis to neurones in the rat nucleus tractus solitarius (NTS) receiving vagal afferent input.
The majority of the putative ‘monosynaptically’ vagal activated cells were inhibited by both MK‐212 (4/6) and DOI (2/4), but unaffected by BW‐723C86 (12/14). In contrast, ‘polysynaptically’ activated NTS cells were excited by both BW‐723C86 (13/19) and DOI (9/10). Inactive ‘intermediate’ cells were inhibited by BW‐723C86 (9/12), MK‐212 (5/6) and DOI (3/4), whilst active cells of this group were excited by BW‐723C86 (7/13) and DOI (5/5).
The selective 5‐HT2B receptor antagonist LY‐202715 significantly reduced the excitatory actions of BW‐723C86 on ‘intermediate’ and ‘polysynaptic’ cells (13/13), but not the inhibitory effects observed on inactive Group 2 cells (n=5) whereas the selective 5‐HT2C receptor antagonist RS‐102221 reversed the inhibitory effects of MK‐212 and DOI on ‘monosynaptic and ‘intermediate’ neurones.
Cardio‐pulmonary afferent stimulation inhibited two of four putative ‘monosynaptically’ activated calls and all four inactive intermediate cells. These were also inhibited by DOI and MK‐212. In contrast, cardio‐pulmonary afferents excited all five active intermediate cells and all six putative ‘polysynaptically’ activated NTS cells, while all were also previously excited by BW‐723C86 and/or DOI.
In conclusion, these data demonstrate that neurones in the NTS are affected differently by 5‐HT2 receptor ligands, in regard of their vagal postsynaptic location, the type of cardio‐pulmonary afferent they receive and the different 5‐HT2 receptors activated.
In in vivo experiments, DOI (a 5‐HT2 receptor agonist), MK‐212 (a 5‐HT2C receptor agonist), and BW‐723C86 (a 5‐HT2B receptor agonist) were applied by ionophoresis to neurones in the rat nucleus tractus solitarius (NTS) receiving vagal afferent input.
The majority of the putative ‘monosynaptically’ vagal activated cells were inhibited by both MK‐212 (4/6) and DOI (2/4), but unaffected by BW‐723C86 (12/14). In contrast, ‘polysynaptically’ activated NTS cells were excited by both BW‐723C86 (13/19) and DOI (9/10). Inactive ‘intermediate’ cells were inhibited by BW‐723C86 (9/12), MK‐212 (5/6) and DOI (3/4), whilst active cells of this group were excited by BW‐723C86 (7/13) and DOI (5/5).
The selective 5‐HT2B receptor antagonist LY‐202715 significantly reduced the excitatory actions of BW‐723C86 on ‘intermediate’ and ‘polysynaptic’ cells (13/13), but not the inhibitory effects observed on inactive Group 2 cells (n=5) whereas the selective 5‐HT2C receptor antagonist RS‐102221 reversed the inhibitory effects of MK‐212 and DOI on ‘monosynaptic and ‘intermediate’ neurones.
Cardio‐pulmonary afferent stimulation inhibited two of four putative ‘monosynaptically’ activated calls and all four inactive intermediate cells. These were also inhibited by DOI and MK‐212. In contrast, cardio‐pulmonary afferents excited all five active intermediate cells and all six putative ‘polysynaptically’ activated NTS cells, while all were also previously excited by BW‐723C86 and/or DOI.
In conclusion, these data demonstrate that neurones in the NTS are affected differently by 5‐HT2 receptor ligands, in regard of their vagal postsynaptic location, the type of cardio‐pulmonary afferent they receive and the different 5‐HT2 receptors activated.
British Journal of Pharmacology (2000) 131, 1445–1453; doi:10.1038/sj.bjp.0703722
DOI: 10.1038/sj.bjp.0703722
View this article