Variable alteration of regional tissue oxygen pressure in rat hippocampus by acute swimming exercise

Abstract

One of the events in the brain is an increasing cerebral blood flow during exercise. The tissue oxygen level may be increased because blood flow correlates with tissue oxygen level. However, it is little known whether the tissue oxygen pressure in hippocampal region (Hip-pO2) will be affected by exercise. AimsThe aim of this study is to examine Hip-pO2 levels in the hippocampus and its changes during exercise. Main methodsWe applied improved Clark-type electrodes to measure Hip-pO2 level in the hippocampus of rats that were subjected to three groups, 2h swimming without weights (low intensity, n=6), 2h swimming with a 5g weight (moderate intensity, n=6), and 2h swimming with a 10g weight (high intensity, n=6). Key findingsExercise affected the Hip-pO2 level, the responses varied with the exercise intensity and duration. Interestingly during and after the Low intensity swimming the Hip-pO2 level showed long lasting enhancement (10–20% above resting level). But the moderate and high intensity swimming increased Hip-pO2 level at the start of the swimming (50%, P<0.05 and slightly above resting level, respectively, at 10min of 2h swimming) and then began to decrease (at 120min and 10min of 2h swimming, respectively), and suppressed the Hip-pO2 levels during post exercise resting period (2h) (85–95% of resting level, NS and 60–70% of resting level P<0.05, respectively). SignificanceWe propose that exercise-induced hippocampal hyper/hypo oxygen condition may participate in beneficial exercise effects on brain function.