Biomedical subjects
Publications and source records attributed to A Sakaguchi.
Acute hypotension and right bundle-branch block occurred when the authors sectioned the uppermost rootlet of the vagus nerve in a case of glossopharyngeal neuralgia. Hypotension lasted for 20 minutes and arrhythmia for 4 days. A possible mechanism is discussed and cardiovascular disorders are reviewed in similar cases.
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Spontaneously hypertensive rats (SHRs) and Wistar Kyoto controls (WKYs) were chronically instrumented for computer-assisted recording of arterial pressure (AP) and heart rate (HR) and examined during classically conditioned emotional (fear) reactions or during the performance of a repertoire of natural behaviors, including eating, drinking, grooming, exploring, and resting. The purpose of the study was to determine whether exaggerated cardiovascular reactivity in SHRs during aversive stimulation: 1) can be coupled to stimuli that before conditioning elicited negligible changes in AP and HR; 2) is accompanied by a proportionately enhanced level of emotional arousal; and 3) is specific to aversive emotional arousal or is also present during natural behaviors. The conditioned blood pressure response (in mm Hg) was greater (p less than 0.01) in SHRs (peak response, 20 +/- 3) than in WKYs (peak response, 7 +/- 1). While the conditioned pressure response was SHRs (peak response, 17 +/- 7 bpm). Behavioral tests indicated reduced emotional reactions in SHRs: SHRs showed less (p less than 0.05) drink suppression (75 +/- 17 sec) than WKYs (111 +/- 10 sec) and SHRs showed less (p less than 0.01) suppression of exploratory activity (201 +/- 40 sec) than WKYs (499 +/- 70) in the presence of the conditioned emotional stimulus. The magnitude of blood pressure changes (in mm Hg) above resting baseline was not different in SHRs and WKYs during eating (SHR, 32 +/- 3; WKY, 28 +/- 2), grooming (SHR, 17 +/- 3; WKY, 14 +/- 2), or exploring (SHR, 17 +/- 2; WKY, 18 +/- 2), but was greater (p less than 0.01) during drinking in SHRs (48 +/- 4) than in WKYs (32 +/- 2). The amount of time (sec) spent grooming (SHR, 55 +/- 23; WKY, 38 +/- 15) and exploring (SHR, 187 +/- 33; WKY, 165 +/- 42) did not differ between the strains, but SHRs spent more time (p less than 0.01) eating (SHR, 1103 +/- 88); WKY, 800 +/- 114) and drinking (SHR, 119 +/- 18; WKY, 32 +/- 12). These findings demonstrate that: 1) exaggerated cardiovascular reactivity in SHRs is readily coupled through conditioning to otherwise benign stimuli; 2) conditioned cardiovascular hyperreactivity is accompanied by a reduced not an enhanced level of conditioned emotional arousal; 3) cardiovascular hyperreactivity is not specific to aversive arousal but is nevertheless a behaviorally-specific mode of response; and 4) SHRs and WKYs differ in the performance of natural as well as emotional behaviors.
This report investigates the contributions of the sympathetic nerves and adrenal medulla to resting mean arterial pressure (MAP) and to emotionally conditioned MAP and heart rate (HR) responses in unrestrained spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive control rats (WKY). Resting MAP (in mm Hg), which was higher in SHR (WKY = 120 +/- 4; SHR = 163 +/- 4; p less than 0.01), did not differ in the two strains following chemosympathectomy (WKY = 105 +/- 2; SHR = 101 +/- 2; n.s.). Adrenal medullectomy did not affect resting MAP in WKY (125 +/- 6; n.s.) but lowered it in SHR (146 +/- 5; p less than 0.05), relative to controls (see above). The conditioned pressor response (in mm Hg) in controls consisted of two peaks (I, II) in both strains, but was exaggerated in SHR (I = WKY, 13 +/- 1; SHR, 25 +/- 2; p less than 0.01; II = WKY 10 +/- 2; SHR 20 +/- 2; p less than 0.01). Chemosympathectomy suppressed (relative to controls) the first peak, but not the second, in both strains (WKY: I = 4 +/- 1, p less than 0.01; II = 12 +/- 2, n.s.; SHR: I = 6 +/- 1, p less than 0.01; II = 15 +/- 2, n.s.). Adrenal medullectomy alone had little effect on the pressor response, but when combined with chemosympathectomy both peaks were largely eliminated (WKY: I = 2 +/- I; II = 5 +/- 1; SHR: I = 1 +/- 0; II = 2 +/- 0). These data indicate that: 1) hypertension in conscious, freely behaving SHR is largely sustained by the sympathetic vasomotor nerves but that the adrenal medulla contributes to the magnitude of the elevation; 2) the early component of the exaggerated pressor response during aversive stimulation is mediated by sympathetic vasomotor excitation; and 3) the later component of the exaggerated pressor response reflects coactivation of the sympathetic vasomotor nerves and the adrenal medulla.
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