Key result
In anesthetized cats, the NO synthase inhibitor L-NNA significantly decreased heart rate and lengthened A-H intervals in intact animals, suggesting a vagal cholinergic mechanism of intrinsic NO.
Intrinsic nitric oxide appears to modulate atrioventricular conduction and sinus rate through a vagal cholinergic mechanism rather than a nonautonomic mechanism.
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No immediate clinical implications in humans; leaves open translation of vagal NO modulation of AV conduction from feline models.
Yabe et al. (1998) studied Cardiac neural regulation (n=22). NG-nitro-L-arginine (L-NNA) vs. Baseline and other experimental groups (denervated, autonomic blockade) was evaluated on Cardiac sympathetic nerve activity, mean arterial pressure, sinus heart rate, and A-H and H-V intervals. In anesthetized cats, the NO synthase inhibitor L-NNA significantly decreased heart rate and lengthened A-H intervals in intact animals, suggesting a vagal cholinergic mechanism of intrinsic NO.
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