Altered regional vasodilator responses to glossopharyngeal nerve stimulation in spontaneously hypertensive rats

The hindlimb and renal vasodilator responses produced by electrical stimulation of the glossopharyngeal nerve were examined in adult (six to eight months) male spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) normotensive rats to ascertain whether central neurogenically activated vasodilator capacity of these regional vascular beds is altered in SHR. Changes in systemic blood pressure and regional blood flow were simultaneously measured, and vascular resistance was calculated. Glossopharyngeal nerve stimulation (3.0 volts, 0.3 ms) at the frequency of 10 Hz resulted in a significantly greater vasodilation (% decrease in resistance) in SHR than in WKY control for both the hindlimb (SHR - 13.0 +/- 1.5% versus WKY - 3.4 +/- 1.6%, P less than 0.01) and renal (SHR - 7.6 +/- 0.6% versus WKY - 1.3 +/- 0.4%, P less than 0.01) vascular beds. The linear portion of the frequency-response curves of hindlimb or renal vasodilation of SHR was shifted parallel to the left of the WKY curve. Stimulus frequencies required to produce a 20% reduction in hindlimb resistance and a 10% reduction in renal resistance were lower in SHR (hindlimb 17.0 +/- 1.8 Hz; renal 19.9 +/- 1.4 Hz) than in WKY control (hindlimb 24.6 +/- 1.1 Hz; renal 39.3 +/- 4.8 Hz; P less than 0.01). The maximal vasodilator response to glossopharyngeal nerve stimulation in the hindlimb vascular bed was similar in SHR and WKY control, but in the renal vascular bed SHR showed a greater maximal response compared to WKY normotensives (SHR - 16.3 +/- 0.9% versus WKY - 12.7 +/- 1.6%, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)