title: Characterization of outward currents in interstitial cells from the guinea pig bladder.
abstract: OBJECTIVE
  Outward currents were characterized from cells resembling interstitial cells of Cajal (ICCs) isolated from the detrusor of the guinea pig bladder.
  
  
  METHODS
  ICC-like cells were studied using the whole cell patch clamp technique and K+ filled pipettes. Outward currents were evoked by stepping positively from a holding potential of -80 mV.
  
  
  RESULTS
  ICC-like cells were distinguished from smooth muscle cells by the presence of lateral branches and an inability to contract spontaneously or when depolarized. Depolarization elicited large outward currents. Penitrem A, a blocker of large conductance, Ca activated K+ channels, significantly decreased the outward current. Its Ca dependence was demonstrated by significant inhibition with nifedipine and Ca-free solution. When large conductance, Ca activated K+ and Ca currents were blocked with penitrem A and nifedipine, a voltage dependent current was unmasked, which activated positive to -50 mV and displayed voltage dependent inactivation with half-maximal inactivation occurring at -71 mV. It was blocked in concentration dependent fashion by tetraethylammonium but unaffected by 4-aminopyridine, charybdotoxin or apamin, suggesting that small and intermediate conductance, calcium activated potassium channels, and Kv1.2 and Kv1.3 channels are unlikely to be involved. At maximal concentrations of tetraethylammonium a portion of the voltage dependent K+ current remained that was not affected by any of the blockers tested.
  
  
  CONCLUSIONS
  ICC-like cells from the detrusor possess calcium activated and voltage dependent K+ currents.
authors.affiliation: Centre for Biophotonics, University of Strathclyde, 27 Taylor Street, Glasgow G4 0NR, Scotland, United Kingdom. karen.mccloskey@strath.ac.uk
authors.forename: Karen D
authors.initials: KD
authors.lastname: McCloskey
mesh_terms: D000200:Action Potentials; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006168:Guinea Pigs; D009183:Mycotoxins / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology* / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D009183:Mycotoxins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C003626:tremortin; D019789:Tetraethylammonium