Abstract
To determine whether the α-dendrotoxin (α-DTX)-sensitive current [D current, slow inactivating transient current (ID)] contributes to the modification of neuronal function in small-diameter adult rat trigeminal ganglion (TG) neurons insensitive to 1 μM tetrodotoxin (TTX), we performed two different types of experiments. In the voltage-clamp mode, two distinct K+ current components, a fast inactivating transient current (IA) and a dominant sustained current (IK), were identified. α-DTX (0.1 μM), ranging from 0.001 to 1 μM, maximally decreased IA by approximately 20% and IK by approximately 16.1% at a +50-mV step pulse, and 0.1 μM α-DTX application increased the number of action potentials without changing the resting membrane potential. Irrespective of the absence and presence of 0.1 μM α-DTX, applications of 4-aminopyridine (4-AP; 0.5 mM) and tetraethylammonium (TEA; 2 mM) inhibited approximately 50% inhibition of IA and IK, 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 μM α-DTX. TEA prolonged the duration of action potentials in the absence or presence of 0.1 μM α-DTX. These results suggest that ID contributes to the modification of neuronal function in adult rat TTX-resistant TG neurons, but after the loss of ID due to 0.1 μM α-DTX application, 4-AP (0.5 mM) and TEA (2 mM) still regulate the intrinsic firing properties of action potential number and shape.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.084988.
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ABBREVIATIONS: α-DTX, α-dendrotoxin; 4-AP, 4-aminopyridine; DRG, dorsal root ganglion; TG, trigeminal ganglion; TTX-R, tetrodotoxin resistance; TTX, tetrodotoxin; TEA, tetraethylammonium; 1–3T, 1 to 3 times threshold; NMDG, N-methyl d-glucamine; I-V, current-voltage; DDP, duration of depolarizing phase of action potentials; RMP, resting membrane potential.
- Received February 15, 2005.
- Accepted April 8, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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