Key result
4-Aminopyridine increases chronotropic and inotropic responses to parasympathetic stimulation and chronotropic fade in isolated atria.
Why the study?
The modulation of the fade response to parasympathetic nerve stimulation in the isolated dog atrium was not fully understood.
The study suggests that the fade response to parasympathetic nerve stimulation is modulated at the parasympathetic nerve terminals in the isolated dog atrium.
Answers are grounded in this paper and cite their sources.
No clinical implications from isolated canine atria; leaves open mechanistic exploration of 4-aminopyridine on parasympathetic responses.
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.
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Furukawa et al. (1986) studied this question. 4-Aminopyridine vs. Control values was evaluated on Fade response to vagal nerve stimulation (chronotropic and inotropic responses). 4-Aminopyridine increased the maximum values of chronotropic and inotropic responses to parasympathetic nerve stimulation in the isolated dog atrium, and increased the fade of the chronotropic response.
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