The influence of nicardipine and ifenprodil on the brain free arachidonic acid level and behavior in hypoxia-exposed rats.

1. The effects of the calcium channel blockers, nicardipine and ifenprodil, on the brain free arachidonic acid level and learning ability in rats exposed to hypoxia were examined. 2. Adult rats were injected with 0.003; 0.01; 0.03; 0.1; 0.3 or 1.0 mg/kg of tested drugs i.p. Thirty min later the learning ability was tested in a passive avoidance task according to the step-through procedure. Immediately after the training trial, the animals were subjected to a period of oxygen deprivation hypoxia until the loss of the righting reflex. The retention trial was carried out 24 hr later. 3. The other groups of animals were pretreated with mentioned substances before hypoxia-exposure. Fifteen min after the loss of the righting reflex they were decapitated and brains were frozen in liquid nitrogen. The brain free arachidonic acid level was quantified by gas chromatography. 4. Both nicardipine and ifenprodil were effective in preventing a memory decline in hypoxia-exposed rats but did not prevent the accumulation of the brain free arachidonic acid in hypoxia-exposed rats. 5. The protective effects of both substances in behavioral studies during acute brain damage caused by hypoxia could not be explained by the prevention of the increase of the brain free arachidonic acid, but by some other mechanism.