AJP - Heart and Circulatory Physiology, Vol 244, Issue 2 239-H246, Copyright © 1983 by American Physiological Society
Rat brain interstitial fluid pressure measured with micropipettes
H. Wiig and R. K. Reed
Interstitial fluid pressure (IFP) in the rat brain has been measured with
micropipettes, 2-4 microns in diameter, after trepanation and incision of
dura. IFP was compared with cerebrospinal fluid pressure (CSFP) measured by
a 0.3-mm (OD) cannula in the lateral ventricle. Control IFP averaged 3.43
+/- 0.65 (SD) mmHg (n = 83) with a corresponding CSFP of 3.53 +/- 0.71 (n =
83). Pretreatment with indomethacin to reduce inflammation during
preparation did not affect IFP and CSFP. Infusion of a 20% mannitol
solution amounting to 5% of body weight resulted in an average IFP of -5.66
mmHg and CSFP of -4.56 mmHg 20 min after start of the infusion, after which
a gradual rise in both pressures was observed. Similar results were
obtained after infusion of hypertonic urea. Inflation of a cuff around the
rat neck resulted in an immediate and similar rise in IFP and CSFP.
Increasing the arterial CO2 partial pressure to 80 mmHg increased IFP to
12-14 mmHg and pial venular pressure to 13-15 mmHg, while CSFP rose to
about 10 mmHg. The micropuncture technique for measurement of brain IFP is
rapid and practically atraumatic and may be used in a variety of animals.
