Purpose: Effects of agents modifying K+ channel activity on the response of the isolated mouse vas deferens to electrical field stimulation (EFS) were investigated. Methods: The experiments were performed in organ baths containing Krebs solution aerated with 95% O2 and 5% CO2 at the temperature of 25°C. The responses were recorded by isotonic transducers (Ugo Basile, 7006) on the paper of polygraph (Ugo Basile, Gemini 7070). Results: 0.1 Hz EFS evoked reproducible twitches while stimulation at 2 Hz and 5 Hz induced frequency-dependent reproducible contractures. Tetraethylammonium (TEA; 50-500 µM),4-aminopyridine (4-AP; 10-200 µM) and charybdotoxin (CHTX; 0.23 µM) caused enhancements in both twitch and contracture amplitudes in a concentration dependent manner. 1 µM Cromakalim decreased twitch activity without significantly affecting the contractures. Glibenclamide at low concentrations (5 nM, 0.1, 1 and 10 µM) affected neither twitch amplitude nor contracture. At higher concentrations (50 and 100 µM), it caused a considerable inhibition in the responses to EFS. 10 µM GLB potentiated the inhibition produced by 1 µM cromakalim on twitch responses. The inhibitory actions of cromakalim (1 µM) and GLB (10 µM) on the contractile activity deepened in the medium with moderately high potassium (10 or 12 mM). Conclusion: These results suggest that CRO-sensitive K+ channels may be insensitive to blocking effect of GLB and they may have voltage-dependent properties in the mouse vas deferens; the GLB action observed at the higher concentrations may have resulted from other mechanisms responsible for CRO action
