Sharpe AL, Calderon AS, Andrade MA, Cunningham JT, Mifflin
SW, Toney GM.
Am J Physiol Heart Circ Physiol. 2013 Dec;305(12):H1772-80.
This is a very slightly older paper from some of the same
people I posted about last weekend. They were still looking to see how chronic
intermittent hypoxia (CIH) could affect lumbar and renal sympathetic nerve
activity (LSNA and RSNA), based on the existing theory that CIH causes
hyperactivity of the chemoreflex, and the changes happen by way of the
paraventricular nucleus (PVN). This time, the parameters of the CIH were: O2 levels
were reduced to 10% for 6 minutes, 10x per hour, for 8 hours a day, for 7
consecutive days.
In this study they found that, compared to control rats, CIH
rats had significantly higher MAP by day 3, with differences in heart rate not
reaching significance. Rats exposed to 7 days of CIH had a greater reduction in
MAP after ganglionic blockade (hexamethonium) than was seen in control rats,
which indicated that CIH rats have increased sympathetic tone. Furthermore, muscimol
inactivation of PVN caused greater reductions of lumbar SNA and MIP in CIH rats
than controls, which also supports the idea that CIH rats have higher sympathetic
tone. Furthermore, when CIH rats were given hypertonic saline directly in to
the carotid artery, they showed a larger increase in LSNA (but not in RSNA)
than control rats did. This suggests that there may be a greater LSNA responsiveness
in CIH rats, and NOT a blunted/ceiling effect due to the higher SNA tone. This
is also interesting on the basis that it adds more data to the idea of
differential control of SNA. -DH
No comments:
Post a Comment