title: Effects of 4-aminopyridine and tetraethylammonium on relaxant responses of isolated dog coronary arteries to 2-nicotinamidoethyl nitrate (SG-75).
abstract: Effects of 4-aminopyridine (4-AP) and tetraethylammonium (TEA) on vasodilator actions of 2-nicotinamidoethyl nitrate (SG-75) were investigated using isolated dog coronary arteries. SG-75 10(-8)--10(-4) Gm/ml produced concentration-dependent relaxations of coronary arterial strips which were contracted with potassium 30 mM or prostaglandin (PG) F2 alpha 10(-6) Gm/ml. Both 4-AP 5 x 10(-4) Gm/ml and TEA 1.6 x 10(-3) Gm/ml produced further contractions of the strips under potassium or PGF 2 alpha contracture. The potency to constrict the strips was greater in 4-AP than in TEA. 4-AP 5 x 10(-4) Gm/ml and TEA 1.6 x 10(-3) Gm/ml did not affect the SG-75-induced relaxations of the strips under potassium-contracture, but significantly depressed them under PGF2 alpha-contracture. In the strips under a resting state, 4-AP 5 x 10(-4) Gm/ml increased tension and produced oscillations in their contractions, but TEA 1.6 x 10(-3) Gm/ml did not. Results suggest that SG-75 may display its relaxant effect on isolated dog coronary arteries in part through an increase in potassium conductance.
mesh_terms: D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects; D015237:Dinoprost; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D020108:Nicorandil; D009566:Nitrates / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D000631:Aminopyridines; D009566:Nitrates; D011460:Prostaglandins F; D013757:Tetraethylammonium Compounds; D009536:Niacinamide; D020108:Nicorandil; D015237:Dinoprost; D015761:4-Aminopyridine; D011188:Potassium