Fig. 6.

Spike train model produces greater release of NA than tonic drive model. Spike train model produces greater release of NA than tonic drive model. Experimental recordings of membrane potential (V_M) in an MVC_like sympathetic preganglionic neurone in a normotensive (WKY; (A)) and spontaneously hypertensive (SH; (B)) (Briant et al., 2014) were used to drive contraction in the SMC model. The WKY cell fired at an average frequency of 1.6 Hz and the SH cell at 4.6 Hz. Both recordings exhibit respiratory modulation, with increases in firing frequency entrained to PNA (lower trace; shaded region). The response of the model to these patterns was compared to tonic stimulation at the same average firing frequency. The NA released in response to the bursting spike train, was greater than tonic, for both the WKY (A₂) and SH (B₂) recording. The release of NA was entrained to respiration. The contractile response was greater in response to the bursting spike trains, but was greatest in response to the SH spike train. (C) Steady-state contractile response of SMC model (% of maximum) to $n=5$ WKY spike trains (square) and $n=5$ SH spike trains (circle). The response to tonic stimulation at the same average firing frequency is also shown (dashed line).