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-pO 2 ) will be affected by exercise. Aims The aim of this study is to examine Hip-pO 2 levels in the hippocampus and its changes during exercise. Main methods We applied improved Clark-type electrodes to measure Hip-pO 2 level in the hippocampus of rats that were subjected to three groups, 2 h swimming without weights (low intensity, n = 6), 2 h swimming with a 5 g weight (moderate intensity, n = 6), and 2 h swimming with a 10 g weight (high intensity, n = 6). Key findings Exercise affected the Hip-pO 2 level, the responses varied with the exercise intensity and duration. Interestingly during and after the Low intensity swimming the Hip-pO 2 level showed long lasting enhancement (10–20% above resting level). But the moderate and high intensity swimming increased Hip-pO 2 level at the start of the swimming (50%, P  2 levels during post exercise resting period (2 h) (85–95% of resting level, NS and 60–70% of resting level P  Significance We propose that exercise-induced hippocampal hyper/hypo oxygen condition may participate in beneficial exercise effects on brain function.