5-Hydroxytryptamine directly inhibits neuronal nicotinic acetylcholine receptors in rat trigeminal ganglion neurons.
In the present study, whole-cell patch clamp recording technique was used to investigate the action of 5-hydroxytryptamine (5-HT) on the function of native neuronal nicotinic acetylcholine receptors expressed in the rat trigeminal ganglion neurons. Inward currents (I(nic)) caused by externally-applied nicotine were observed in majority of the examined neurons, which were mediated by alpha-bungarotoxin-insensitive nicotinic acetylcholine receptors. We found that 5-HT could reversibly inhibit I(nic) in a concentration-dependent manner, and the inhibition did not involve 5-HT receptors. Other serotonergic agents, such as 2-methyl-5-HT, alpha-methyl-5-HT, sumatriptan and ICS-205,930, also had similar inhibitory effects on I(nic). 5-HT inhibited nicotinic acetylcholine receptors in a non-competitive manner, as 5-HT decreased the maximal current response to nicotine but had no effect on the threshold and EC(50). The inhibition of I(nic) by 5-HT was voltage-dependent and became stronger at hyperpolarized potentials. These results indicated that 5-HT directly inhibited nicotinic acetylcholine receptors in the trigeminal ganglion neurons. As a local modulator of the nicotinic acetylcholine receptor, 5-HT might play a role in the modulation of sensory information.
Hu
Wang-Ping
WP
Department of Physiology, Xianning College, Xianning 437100, PR China. wangping_hu@yahoo.com
Ma
Shi-Yu
SY
Wu
Ji-Liang
JL
Li
Zhi-Wang
ZW
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D008564:Membrane Potentials / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000502:physiology; D011985:Receptors, Serotonin / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D012668:Trigeminal Ganglion / Q000187:drug effects* / Q000502:physiology
D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D011985:Receptors, Serotonin; D012701:Serotonin; D009538:Nicotine