Tachykinins cause inward current through NK1 receptors in bullfrog sensory neurons

Brain Res. 1996 Mar 25;713(1-2):160-7. doi: 10.1016/0006-8993(95)01506-x.


The effects of tachykinins on primary afferent neurons of bullfrog dorsal root ganglia (DRG) were examined by using whole-cell patch-clamp methods. Neurokinin A (NKA) caused inward current (INKA) in a concentration-dependent manner. Concentration-response curve showed that the EC50 for NKA was 6 nM. The INKA showed strong tachyphylaxis, when NKA was continuously applied for more than 1 min. Substance P (SP) also produced inward current with potency similar to that of NKA. Neurokinin B (NKB) was less effective in producing the inward current. The order of agonist potency was NKA = SP >> NKB. Spantide ([D-Arg1, D-Trp7.9, Leu11]SP), a non-selective peptide antagonist at tachykinin receptors, reduced the tachykinin-induced current. CP-99,994, a selective non-peptide antagonist for neurokinin-1 (NK1) receptor, inhibited the inward currents produced by NKA and SP. The INKA was associated with decrease in K+ conductance. NKA suppressed both a voltage-dependent K+ current, the M-current (IM), and a voltage-independent background K+ current, IK(B). Intracellular dialysis with GTP gamma S (100 nM) or GDP beta S (100 microM) depressed the INKA. Pre-treatment of DRG neurons with pertussis toxin (PTX) did not prevent the INKA. Depletion of intracellular ATP depressed the INKA. These results suggest that the tachykinin-induced inward current is mediated through the NK1 receptor which mainly couples to PTX-insensitive G-protein in bullfrog primary afferent neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Barium / pharmacology
  • Dose-Response Relationship, Drug
  • Ganglia, Spinal / drug effects*
  • Membrane Potentials / drug effects*
  • Neurons / drug effects*
  • Potassium / pharmacology
  • Rana catesbeiana
  • Receptors, Neurokinin-1 / drug effects*
  • Tachykinins / pharmacology*


  • Receptors, Neurokinin-1
  • Tachykinins
  • Barium
  • Potassium