Arterial chemoreflex in conscious normotensive and hypertensive adult rats

Evidence from human and animal studies suggests that the arterial chemoreflex may be exaggerated in essential hypertension. In the present study, cardiorespiratory responses to peripheral chemoreceptor stimulation were compared in conscious unrestrained spontaneously hypertensive (SH) and normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats (13-14 wk old). Chemoreceptors were stimulated by injections of potassium cyanide (30-125 microgram/kg iv). Chemoreceptor stimulation elicited a pressor response and bradycardia. The peak change in mean arterial pressure evoked during chemoreceptor stimulation was not significantly different between SH (n = 18) and WKY (n = 18) rats but was significantly smaller in SD rats (n = 18). An evaluation of respiratory responses to chemoreceptor stimulation in conscious and anesthetized rats also demonstrated no significant difference between SH and WKY rats, but the response of the SD rats tended to be smaller. These results demonstrate that differences in the arterial chemoreflex response of SH vs. normotensive rats are not linked to hypertension but, rather, to differences between rat strains.