Histamine activates whole cell K+ currents in swine carotid arterial smooth muscle cell

1. The effects of histamine on whole cell K+ currents were evaluated in cultured smooth muscle cells that were derived from explants of swine carotid artery. These cells exhibited cytoplasmic protein and agonist-induced calcium responses typical of noncultured smooth muscle cells. 2. Upon obtaining whole cell configuration, depolarization from a holding potential of -80 mV elicited a slowly inactivating voltage-dependent outward current that was sensitive to tetraethylammonium and 4-aminopyridine. 3. These K+ currents were at least partially Ca2+ dependent since they were inhibited by extracellular bath application of verapamil or by substitution of external Ca2+ with Co2+. 4. The addition of extracellular histamine increased the outward current both in the presence and absence of extracellular Ca2+ and this response was blocked by (+/-)chlorpheniramine. 5. We conclude that swine carotid arterial smooth muscle cells exhibit voltage and calcium dependent potassium current and that these currents are modified by histamine stimulation.