Effects of alpha-dendrotoxin on K+ currents and action potentials in tetrodotoxin-resistant adult rat trigeminal ganglion neurons.
To determine whether the alpha-dendrotoxin (alpha-DTX)-sensitive current [D current, slow inactivating transient current (I(D))] contributes to the modification of neuronal function in small-diameter adult rat trigeminal ganglion (TG) neurons insensitive to 1 microM tetrodotoxin (TTX), we performed two different types of experiments. In the voltage-clamp mode, two distinct K+ current components, a fast inactivating transient current (I(A)) and a dominant sustained current (I(K)), were identified. Alpha-DTX (0.1 microM), ranging from 0.001 to 1 microM, maximally decreased I(A) by approximately 20% and I(K) by approximately 16.1% at a +50-mV step pulse, and 0.1 microM alpha-DTX application increased the number of action potentials without changing the resting membrane potential. Irrespective of the absence and presence of 0.1 microM alpha-DTX, applications of 4-aminopyridine (4-AP; 0.5 mM) and tetraethylammonium (TEA; 2 mM) inhibited approximately 50% inhibition of I(A) and I(K), respectively. 4-AP (0.5 mM) depolarized the resting membrane potential and increased the number of action potentials in the absence or presence of 0.1 microM alpha-DTX. TEA prolonged the duration of action potentials in the absence or presence of 0.1 microM alpha-DTX. These results suggest that I(D) contributes to the modification of neuronal function in adult rat TTX-resistant TG neurons, but after the loss of I(D) due to 0.1 microM alpha-DTX application, 4-AP (0.5 mM) and TEA (2 mM) still regulate the intrinsic firing properties of action potential number and shape.
Yoshida
Shinki
S
Department of Physiology, Nippon Dental University, School of Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan. shinki@tokyo.ndu.ac.jp
Matsumoto
Shigeji
S
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D002478:Cells, Cultured; D004351:Drug Resistance; D004546:Elapid Venoms / Q000494:pharmacology*; D004594:Electrophysiology; D009474:Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology*; D012668:Trigeminal Ganglion / Q000166:cytology* / Q000187:drug effects
D004546:Elapid Venoms; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013779:Tetrodotoxin; D019789:Tetraethylammonium; C020273:dendrotoxin