title: Effects of simple indoles, noradrenaline, nicotine, and tyramine on action potential and contractility of the isolated guinea-pig papillary muscle.
abstract: 1. Simultaneous recordings of both the transmembrane action potential and the contractions were made in isolated electrically driven papillary muscles of the guinea pig in order to compare the effects of 6-methoxyindole (6-MOI), 3-methylindole (3-MI) and 5-methylindole (5-MI) with those of noradrenaline (1.2 - 10(-6) M), nicotine (2 - 10(-5) M), and tyramine (5.8 - 10(-6) M). 2. Noradrenaline, nicotine, tyramine and 6-MOI (5.4 - 10(-4) M) enhanced the contractility whilst 3-MI (3.8 and 7.8 - 10(-4) M) and 5-MI (1.9 and 3.8 - 10(-4) M) had only irregular effects. The active compounds shortened and time-to-peak tension and increased the rate of relaxation. 3. The duration of the action potential was prolonged by noradrenaline, nicotine, and tyramine, but shortened by 3-MI, 5-MI, and 6-MOI. 4. The results showed that the effect of drugs on the action potential are not necessarily linked to those on contractility.
mesh_terms: D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*; D009538:Nicotine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology*; D010210:Papillary Muscles / Q000187:drug effects; D012110:Reserpine / Q000494:pharmacology; D013997:Time Factors; D014439:Tyramine / Q000494:pharmacology*
chemical_list: D007211:Indoles; D009538:Nicotine; D012110:Reserpine; D009638:Norepinephrine; D014439:Tyramine