Time-dependent effect of sectioning carotid sinus nerves on the vagally mediated baroreflex

Abstract

The purpose of the reported experiments was to examine whether the vagally mediated baroreflex system (V-system) increases its feedback gain with time after sectioning of the carotid sinus nerves (CSN). In 10 dogs anesthetized with Nembutal, we determined the overall open-loop gain (G) of the rapidly acting arterial pressure control system. G was assessed as (delta API/delta APs)-1, where delta API and delta APs represent the immediate and steady-state decreases in arterial pressure at the aortic arch following a fast step-wise reduction in blood volume. delta API, delta APs and GINTACT in the intact condition (30th min before sectioning of the CSN) were -1.8 +/- 0.1 kPa, -0.20 +/- 0.01 kPa and 8.4 +/- 0.3 (mean +/- SE), respectively. The mean values of delta API, delta APs and G after sectioning of the CSN (Gv), first averaged within individual dogs and then averaged for ten dogs, were -2.53 +/- 0.07 kPa, -1.1 +/- 0.05 kPa, and 1.5 +/- 0.1, respectively. Gv did not change with time over about 4 h after sectioning of the CSN. It is concluded that the V-system cannot augment its ability to restore arterial pressure in compensation for the lost function of the carotid sinus baroreflex system over 4 h after sectioning of the CSN in the anesthetized dog.

Temporal and spatial interactions between the carotid sinus and vagally mediated baroreflexes in dogs.

“…The validity of the quick mild hemorrhage method to estimate the gain of the vagally mediated baroreflex system has been described by KAIZUKA et al (1985). Employing the same method, the gain has been reported previously to be 1.5 (KAIzu cA et al, 1985) and 1.8 (HosoMl et al, 1981).…”