Figure 3

Capsaicin-sensitive baroreceptor. Capsaicin (1 μM) depressed the pressure-discharge response of an irregular aortic BR. The discharge properties including high coefficient of variation (COV = 9.9) of discharge, low discharge rate (maximum of 40 Hz) and low slope-sensitivity – all characteristic of C-fiber BRs. Pressure was ramped from 40 – 160 mmHg at a rate of 1 mmHg/sec. CAP progressively interrupted discharge with intermittent drops in discharge rates to half or less the prevailing rate (points at high pressures falling below the general trend). At 10 min and beyond, the BR failed to respond to suprathreshold pressures and at 15 min the relation was completely blocked. The loss of individual instantaneous frequency points by discrete increments (integer reciprocals, e.g ½. 1/3, etc.) indicates likely conduction block.