Asynchronous action potential discharge in human muscle sympathetic nerve activity.

Asynchronous action potential discharge in human muscle sympathetic nerve activity. Am J Physiol Heart Circ Physiol. 2019 Aug 02;: Authors: Klassen SA, Moir ME, Limberg JK, Baker SE, Nicholson WT, Curry TB, Joyner MJ, Shoemaker JK Abstract What strategies are employed by the sympathetic system to communicate with the circulation? Muscle sympathetic nerve activity (MSNA) occurs in bursts of synchronous action potential (AP) discharge, yet whether between-burst asynchronous AP firing exists remains unknown. Using multi-unit microneurography and a continuous wavelet transform to isolate APs, we studied AP synchronicity within human MSNA. Asynchronous APs were defined as those which occurred between bursts. Experiment One quantified AP synchronicity in eight individuals at baseline (BSL), -10 mmHg lower body negative pressure (LBNP), -40 mmHg LBNP, and end-expiratory apnea (APN). At BSL, 33 ± 12 % of total AP activity was asynchronous. Asynchronous discharge was unchanged from BSL (67 ± 37 AP/min) to -10 mmHg LBNP (69 ± 33 AP/min), -40 mmHg LBNP (83 ± 68 AP/min), or APN (62 ± 39 AP/min). Across all conditions, asynchronous AP probability and frequency decreased with increasing AP size. Experiment Two examined the impact of the ganglia on AP synchronicity using nicotinic blockade (trimethaphan). The largest asynchronous APs were de-recruited from BSL (11 ± 4 asynchronous AP clusters) to the last minute of the trimethaphan infusion w...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research