Characterization of 5-HT3 receptors of N1E-115 neuroblastoma cells by use of the influx of the organic cation [14C]-guanidinium.
1. The 5-HT3 receptor-mediated cation influx into N1E-115 mouse neuroblastoma cells has been studied by the use of the organic cation [14C]-guanidinium. 2. 5-Hydroxytryptamine (5-HT, 30 microM) caused a time-dependent influx of [14C]-guanidinium which, in contrast to the influx elicited by veratridine (100 microM), was not inhibited by tetrodotoxin (TTX, 10 microM). The 5-HT-induced influx was potentiated by substance P and inhibited by ondansetron. 3. 5-HT and the selective 5-HT3 receptor agonists, m-chloro-phenylbiguanide, phenylbiguanide and 2-methyl-5-HT caused bell-shaped concentration-response curves; the rank order of potency was m-chloro-phenylbiguanide > 5-HT > phenylbiguanide = 2-methyl-5-HT. Among these agonists, 5-HT elicited the highest influx of [14C]-guanidinium. 5-Methoxytryptamine, an agonist at 5-HT4 receptors, showed no effect. 4. The [14C]-guanidinium influx induced by 100 microM 5-HT was not affected by methysergide (10 microM) and ketanserin (10 microM) but was inhibited by 5-HT3 receptor antagonists with the following rank order of potency: ICS 205-930 > ondansetron > MDL 72222 >> metoclopramide. 5. The 5-HT-induced [14C]-guanidinium influx was increased in the absence of Ca2+ and/or Na+ and by a reduction of the temperature from 36 degrees to 20 degrees C. 6. Preincubation with 5-HT (100 microM) caused a time-dependent and rapidly reversible decrease of the 5-HT-induced [14C]-guanidinium influx. 7. It is concluded that [14C]-guanidinium influx measurement in N1E-115 cells is a convenient method to study properties of the cation channel of the 5-HT3 receptor. This influx is independent of the fast sodium channel.
Bönisch
H
H
Institut für Pharmakologie und Toxikologie, Universität Bonn, Germany.
Barann
M
M
Graupner
J
J
Göthert
M
M
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002250:Carbon Radioisotopes; D019791:Guanidine; D006146:Guanidines / Q000378:metabolism*; D051379:Mice; D009447:Neuroblastoma; D009474:Neurons / Q000737:chemistry* / Q000187:drug effects; D011869:Radioligand Assay; D011985:Receptors, Serotonin / Q000032:analysis* / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists; D012964:Sodium / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology; D013696:Temperature; D013779:Tetrodotoxin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014701:Veratridine / Q000494:pharmacology
D002250:Carbon Radioisotopes; D006146:Guanidines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D013373:Substance P; D013779:Tetrodotoxin; D014701:Veratridine; D012964:Sodium; D019791:Guanidine; D002118:Calcium