Effects of
lidocaine on parameters of membrane functional integrity were investigated in the mouse brain. Changes in the direct-current potential shift in the cerebral cortex provoked by
decapitation ischemia were compared in animals given
lidocaine (0.05, 0.25, or 1.0 micromol, intracerebroventricular) or saline 15 minutes before
ischemia. The brain content of
adenosine 5'-triphosphate (
ATP) was measured in animals subjected to 0, 0.5, 1, and 2 minutes of
decapitation ischemia, and the effect of preischemic administration of
lidocaine (0.25 micromol, intracerebroventricular) was evaluated. Na+, K+-
ATPase, and Ca2+-
ATPase activity was evaluated in brains pretreated with
lidocaine (0.25 micromol, intracerebroventricular) or saline 15 minutes before
decapitation. Changes in the intracellular Ca concentration ([Ca2+]i) were evaluated in hippocampal slices and the effects of
lidocaine (50, 100, or 400 microM) were assessed in the hippocampal CA1 field and dentate gyrus at pH 7.4 and pH 6.8 every 60s for a duration of 50 min. The preischemic administration of
lidocaine (1.0 and 0.25 micromol) delayed the onset of anoxic depolarization to 49 seconds and 44 seconds, respectively, as compared with that in the saline group at 27 seconds.
Lidocaine maintained
ATP levels higher than those in corresponding saline groups, values being 165% after 1 minute of
ischemia and 212% after 2 minutes, respectively.
Lidocaine did not affect Na+, K+-
ATPase, and Ca2+-
ATPase activity.
Lidocaine did not affect changes in the [Ca2+]i in either area at either pH. The findings may suggest that
lidocaine maintains the energy level by delaying depolarization in neurons, which may contribute to removal of cytosolic Ca2+ in ischemic states.