Baroreflex control of renal sympathetic nerve activity in hypertensive miniature swine

The baroreceptor reflex control of renal nerve activity was examined in seven normotensive and 14 deoxycorticosterone acetate-treated anesthetized Yucatan miniature swine. Pressor responses evoked by the administration of phenylephrine were used to assess reflex control. The mean absolute threshold for inhibition of renal nerve activity was higher but not significantly different between the deoxycorticosterone acetate-treated and normotensive group. However, the mean relative threshold for inhibition of renal nerve activity was significantly greater in the deoxycorticosterone acetate-treated group (p less than 0.05). Responses from five deoxycorticosterone acetate-treated and five normotensive swine were used to examine the time course of the baroreflex inhibition of renal nerve activity. During the initial rise in pressure the percent inhibition of renal nerve activity was similar for the two groups. During the recovery phase of the response, renal nerve activity in the deoxycorticosterone acetate-treated group returned to baseline while renal nerve activity remained attenuated below baseline in the normotensive group. The gain of the reflex was significantly lower in the deoxycorticosterone acetate-treated group compared with the control group (p less than 0.05). The results of this study clearly indicate that baroreceptor reflex control of renal nerve activity is altered in anesthetized deoxycorticosterone acetate-treated hypertensive swine.