Suppressive effects of somatostatin in dog Purkinje fibres.
1. The effects of somatostatin (SS, 1 nM-3 microM) on the electrical and mechanical activities of isolated Purkinje fibres of the dog were studied. 2. In most Purkinje fibres driven electrically in normal [K]o Tyrode solution, SS decreased the force of contraction slightly and had very little effect on the fast response action potential. However, in sensitive fibres SS induced a moderate reduction of action potential duration and contractile force in normal [K]o and depressed the slow response action potentials in high [K]o. 3. In spontaneously beating Purkinje fibres, SS decreased the regular rhythms slightly but abolished bursts of fast rhythms at a concentration as low as 1 nM. 4. When the fibres were depolarized in the presence of 0.2 mM barium or in Na-free solution, SS suppressed the Ca-dependent slow response action potentials. 5. These findings suggest that SS may suppress abnormal automatic activity of dog Purkinje fibres through a reduction of transmembrane Ca influx or a modulation of intracellular calcium.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004110:Diltiazem / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D011188:Potassium / Q000494:pharmacology; D011690:Purkinje Fibers / Q000187:drug effects*; D012964:Sodium / Q000502:physiology; D013004:Somatostatin / Q000494:pharmacology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D013757:Tetraethylammonium Compounds; D013004:Somatostatin; D012964:Sodium; D004110:Diltiazem; D011188:Potassium