EXPRESSION OF TACHYKININ RECEPTORS IN XENOPUS OOCYTES INJECTED WITH POLY(A)(-ROOT GANGLION()RNA FROM CAT DORSAL)

The expression of the types of tachykinin receptors in the dorsal root ganglion (DRG) neurons by means of Xenopus oocyte expressing system w as studied. Poly(A)(+) RNAs were extracted from cat cervical and lumba r DRG. Two days after injection of Poly(A)+ RNAs, the oocytes were rec orded with the two-electrode voltage clamp technique. In the oocytes i njected with DRG poly(A)(+) RNA, [Sar(9),Met(O-2)(11)]-substance P(Sar -SP, 1 mu mol/L), neurokinin A (NKA, 1 mu mol/L) or [beta-Ala(8)]-neur okinin A((4-10))(Ala-NKA, 1 mu mol/L) produced an inward current compr ising a rapid spike and a long sustained oscillatory component for sev eral minutes. Sar-SP induced response was blocked by NK-1 antagonist L -668, 169 (1 mu mol/L), but not by NK-2 antagonist L-659, 877( 1 mu mo l/L). In contrast, Ala-NKA and NKA responses were only blocked by L-65 9, 877. The oocytes injected with DH Poly(A)+ RNA also responded to Sa r-SP and NKA with similar inward currents, which were selectively bloc ked by L-668, 169 and L-659, 877, respectively. These tachykinins-indu ced responses had a potent desensitization. The present data indicate expression of NK-1 and NK-2 receptors in DRG neurons, suggesting that there may be tachykinin autoreceptors on the nociceptive primary affer ent terminals.