Fig. 6.

Average changes in left femoral mean arterial pressure (ΔMAP) evoked through bipolar stimulation of the left ADN using randomly selected pairs of voltage (1–20 V) and frequency (1–100 Hz). A–C: low-intensity (≤2 V), low-frequency (≤20 Hz) stimulation of low-threshold myelinated baroreceptor (BR) afferents evoked a substantial depressor reflex in female rats that was essentially lacking in male rats (see inset). Stimulation frequencies in excess of 30 Hz were necessary to elicit a comparable reflex response from male rats, although one that was significantly less than that from female rats. D: higher intensity (≥5 V) stimulation of the left ADN evoked a depressor reflex of comparable magnitude from male and female rats at all but the lowest rates (≤2 Hz). Results from the nerve conduction studies suggest that beyond ∼5 V of nerve stimulation there can be graded recruitment of the higher-threshold, unmyelinated BR afferents (see Figs. 2–4), which bring about a depressor response that is quite similar in male and female rats. Data are means ± SD. *P < 0.05, #P < 0.01.