Characteristics of Aortic Baroreceptor C-Fibres in the Rabbit

Publisher Website
Google Scholar
Abstract
The characteristics of 40 C-fibers arising from the aortic arches of 15 normotensive rabbits were investigated. The conduction velocity of the fibers varied between 0.5-1.8 m/s (0.91 .+-. 0.05, mean .+-. SE). The activation threshold for all the fibers lay between 70-140 mmHg. Medullated fibers (32) from the same animals had thresholds between 35 and 90 mmHg. After correction for the time delay in conduction the firing in the C-fibers occurs in early systole. Pressure response curves were constructed for 10 medullated and 18 C-fibers. The mean activity at 100 mmHg was, for the C-fibers 5.0 Hz and for the medullated fibers 34 Hz. At 130 mmHg the activity in the C-fibers was 13 Hz and in the medullated fibers 68 Hz. C-fibers from the aortic baroreceptor regions are activated at higher pressures than the medullated fibers and have lower discharge frequencies. Noradrenaline [norepinephrine] did not influence the pressure response curves of the C-fibers. The arterial baroreceptor C-fibers may exert a weak tonic influence on the vasomotor center at normal pressures but are likely to be of greater importance when the arterial pressure rises acutely.