Excitability of small-diameter trigeminal ganglion neurons by 5-HT is mediated by enhancement of the tetrodotoxin-resistant sodium current due to the activation of 5-HT4 receptors and/or by the inhibition of the transient potassium current

摘要: The aims of the present study were to investigate whether activation 5-HT receptor subtypes (5-HT(4) and 5-HT(3)) acted significantly on modification tetrodotoxin-resistant sodium current (I(NaR)) in small-sized rat trigeminal ganglion (TG) neurons inhibition transient K(+) (I(A)) contributed excitability those neurons. applications at concentrations ranging from 0.01-10 microM increased peak I(NaR). One micromolar application caused greatest increase I(NaR) amplitude accompanied by a hyperpolarizing shift curve. A similar properties was also obtained via 5-HT(4) agonist, RS 67333, 0.001-1 microM. largest effects (1 microM) 67333 (0.1 abolished pretreatment with ICS 205-930 (a 5-HT(3/4) antagonist, 10 microM), which showed no significant effect baseline However, 30 decrease Phenylbiguanide 5-HT(3) agonist) did not alter when applied 1 100 0.1 decreased approximately 31%. threshold for action potential generation lower after 67333. Furthermore, number potentials resting membrane got more positive, but it duration depolarization phase potential. In addition, neither additional presence forskolin, stimulator adenylyl cyclase, nor opposite forskolin enhancement I(NaR), indicates an 'occluding effect.' These results suggest that 5-HT-induced is mediated receptors, involving cAMP-dependent signaling pathway, I(A) following agonist contributes potentials.