Chonnam Med J.  2002 Mar;38(1):17-23.

Effects of Potassium Channel Modulators on Contractile Responses of Isolated Rat Vas Deferens to Field Stimulation

• Baik YH
• Kim YM
• Rhu BS

Abstract

Apart from regulating the resting membrane potential, K+ channels might also participate in cellular activity in response to endogenous neurotransmitters and exogenous agents. K+ channel modulators including 4 - aminopyridine (4-AP) have been known to control the release of neurotransmitters from the depolarized nerve terminals as a result of opening or blocking K+ channels. The purpose of this study was to investigate effects of K+ channel modulators on the contractile responses induced by electrical field stimulation (EFS) in the isolated vas deferens of the rat. The EFS (20 V, 1 msec duration, 20 Hz, for 2 sec every 2 min) produced a transient and reproducible contraction (EFS-contraction) in the isolated vas deferens. EFS-contraction was inhibited by levcromakalim and the inhibition recovered by 4-AP. Non-specific K+-channel blockers, 3,4-diaminopyridine (3,4-DAP) and 4-AP markedly potentiated EFS- contraction (AP-induced potentiation), but another derivative of aminopyridine 2,6-diaminopyridine (2,6-DAP) did not. Tetraethylammonium (TEA), a K+ channel blocker which differs in molecular structure from AP, slightly inhibited EFS-contraction. EFS-contraction was abolished by removal of Ca2+ from the bathing solution and restored by addition of Ca2+. The AP-induced potentiation was partially inhibited by nifedipine, diltiazem and prazosin, but not affected by yohimbine. The above results suggest that 4-AP potentiates EFS-contraction via blockade of AP-sensitive K+ channel in nerve terminal of the isolated rat vas deferens and that the K+ channels contribute in controlling the release of neurotransmitters from the terminals.

Keyword

Vas deferens; Field stimulation; K+ channel; 4-Aminopyridine

MeSH Terms

4-Aminopyridine
Animals
Baths
Cromakalim
Diltiazem
Membrane Potentials
Molecular Structure
Neurotransmitter Agents
Nifedipine
Potassium Channels*
Potassium*
Prazosin
Rats*
Tetraethylammonium
Vas Deferens*
Yohimbine
4-Aminopyridine
Cromakalim
Diltiazem
Neurotransmitter Agents
Nifedipine
Potassium
Potassium Channels
Prazosin
Tetraethylammonium
Yohimbine