Characteristics of aortic baroreceptor C-fibres in the rabbit.
The characteristics of 40 C-fibres arising from the aortic arches of 15 normotensive rabbits have been investigated. The conduction velocity of the fibres varied between 0.5-1.8 m/s (0.91 +/- 0.05, mean +/- S.E.). The activation threshold for all the fibres lay between 70-140 mmHg. 32 medullated fibres from the same animals had thresholds between 35 and 90 mmHg. After correction for the time delay in conduction the firing in the C-fibres occurs in early systole. Pressure response curves were constructed for 10 medullated and 18 C-fibres. The mean activity at 100 mmHg was, for the C-fibres 5.0 Hz and for the medullated fibres 34 Hz. At 130 mmHg the activity in the C-fibres was 13 Hz and in the medullated fibres 68 Hz. Thus C-fibres from the aortic baroreceptor regions are activated at higher pressures than the medullated fibres and have lower discharge frequencies. Noradrenaline did not influence the pressure response curves of the C-fibres. It is concluded that the arterial baroreceptor C-fibres may exert a weak tonic influence on the vasomotor centre at normal pressures but are likely to be of greater importance when the arterial pressure rises acutely.
D000818:Animals; D001013:Aorta, Thoracic / Q000294:innervation*; D001794:Blood Pressure / Q000187:drug effects; D004558:Electric Stimulation; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D009431:Neural Conduction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits
D009638:Norepinephrine