Tachykinin-induced responses via neurokinin-1 and-3 receptors in hamster submandibular ganglion neurones

Both substance P and neurokinin A art: known as neurotransmitters of the su bmandibular ganglion cell. In this study, the effects of neurokinin (NK) re ceptor-subtype agonists on hamster submandibular ganglion cells were invest igated using the whole-cell patch-clamp technique. Membrane currents evoked by a ramp pulse from +50 to -100 mV (-150 mV/1000 msec) were compared in b oth the absence and presence of NK receptor agonist. The NK-1 receptor agon ist [Sar(9), Met (O-2)(11)]-substance P, the NK-2 receptor agonist [Ala(5), beta-Ala(8)]-alpha-neurokinin fragment 4-10, and the NK-3 receptor agonist senktide were used. The three agonists hose-dependently increased the ampl itude of the inward current with a reversal potential near 0 mV. Their rank order was NK-1 = NK-3 > NK-2. Even when the external solution was replaced with Cs+ or N-methyl-D-glucamine(+) instead of Na+, the NK receptor agonis ts also increased the amplitude of the inward current. Thus, NK-1 and NK-3 receptors are apparently coupled with non-selective cation channels in subm andibular ganglion cells. (C) 1999 Elsevier Science Ltd. All rights reserve d.