Clin Exp Pharmacol Physiol. 2001 Dec;28(12):972-5.
In this study, rabbits either had a clip fixed around one renal artery to induce hypertension (known as the two kidney one clip or 2k1c technique) or were given a sham surgery. The rabbits’ renal sympathetic nerve activity (RNSA) and heart rate (HR) were compared between groups during infusion of drugs to raise or lower blood pressure (phenylephrine and nitroprusside, respectively).
At 3 weeks after surgery, there was a strong reduction in the range/maximum nerve activity during decreases in blood pressure (36% lower than sham controls). However the maximum RSNA returned to levels near sham controls by 6 weeks. The resting point and curves for RSNA and HR were both shifted to the right, suggesting an attenuation in sensitivity in both parameters, at 3 and 6 weeks. This brings up questions in my mind about what structures of the baroreflex are being attenuated - because from a baroreceptor-centric point of view, the interpretation is correct... but from a very RVLM-centric point of view, you might try to argue that the baroreflex is actually being facilitated by 2k1c.
Most interesting is that they say their results conflict with another group's paper showing an INCREASE in maximum RSNA after 2k1c. This was a difference in how the change was quantified. In the other paper, the change was measured as a percent of resting nerve activity, while in this paper it was measured as a percent of the max RSNA activated by a noxious stimulus (smoke). When the authors of this paper adapted the other way of measuring RSNA, they got the same results as the other group. So, how you normalize can make a lot of difference in interpreting your results. - DJH
No comments:
Post a Comment