Figure 3. Measurements of $P_{\mathrm{t}{\mathrm{O}}_2}$ in the caudal NTS of SHRs and Wistar rats under ganglionic blockade.

Animals received a dose of chlorisondamine (1 mg kg⁻¹ i.v.), and mean arterial blood pressure (ABP) levels were normalized to a set value of ∼100 mmHg with an infusion of phenylephrine. A, representative experimental trace showing the effect of electrical stimulation of the cut central end of the left vagus nerve (ESVN) on tissue $P_{{\mathrm{O}}_2}$ ($P_{\mathrm{t}{\mathrm{O}}_2}$). The ESVN caused a biphasic change in $P_{\mathrm{t}{\mathrm{O}}_2}$ in the NTS characterized by an initial dip followed by an overshoot above baseline. Note that during ganglionic blockade, ESVN no longer causes fluctuations in ABP and heart rate (HR). B, group data showing the effect of ESVN at different stimulation frequencies. Data are presented as means ± SD. These changes were compared with control values using a two‐way ANOVA and the means compared with Fisher's LSD test.