Effects of 4-aminopyridine on the fade response to vagal nerve stimulation in the isolated dog atrium.
Intramural parasympathetic nerve stimulation (5 Hz, 2 min) after propranolol treatment evoked negative chronotropic and inotropic responses in the isolated dog atrium. The cardiac responses were not maintained during stimulation; they reached maximum values and then faded back toward their control values ("fade" response). 4-Aminopyridine increased the maximum values of both responses, and it increased the fade of the chronotropic response but not that of the inotropic response. These results suggest that the fade response to parasympathetic nerve stimulation is modulated at the parasympathetic nerve terminals of the isolated dog atrium.
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D004285:Dogs; D006321:Heart / Q000187:drug effects* / Q000294:innervation; D006325:Heart Atria; D006339:Heart Rate / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D014630:Vagus Nerve / Q000187:drug effects*
D000631:Aminopyridines; D015761:4-Aminopyridine