Is there a preferential loss of aortic baroreceptor C‐fibre activity during the development of atherosclerosis?

Atherosclerosis is associated with hypertension and poorer regulation of arterial blood pressure. Arterial pressure is detected by baroreceptors in the aortic arch and carotid bifurcation; regions that are affected by atherosclerosis. We generated atherosclerosis in New Zealand White rabbits by feeding a diet containing 6% fat and 0.5% cholesterol from 7 weeks of age. After 14 weeks on the diet we examined the arterial baroreceptor response to ramps of arterial pressure, and quantified atherosclerotic lesions in the aortic arch. In atherosclerotic animals, at arterial pressures greater than 100 mmHg, integrated aortic nerve activity (IANA) was significantly less than in control animals. The lower IANA recorded in the atherosclerotic animals at higher pressures correlated with intima‐media thickening in the aortic arch. Baroreceptors are coupled to either A‐ or C‐ afferent fibre; each type responds differently to aortic blood pressure. Much of the activity at higher pressures is attributable to C‐fibres, which suggests that in our model of atherosclerosis there may be a preferential loss of C‐fibre activity accompanying changes in the intima‐media. This study was supported by the Otago Medical Research Foundation, the Otago Research Grants and the Department of Physiology, University of Otago.