BEHAVIORAL EVIDENCE FOR THE EXISTENCE OF 2 POOLS OF CELLULAR INOSITOL

Lithium reduces brain inositol levels by inhibiting inositol monophosp hatase. In a previous study it was found that administration of piloca rpine to Li-treated rats causes limbic seizure behavior which can be r eversed by i.c.v. myo-inositol but not chiro-inositol, suggesting that this behavior is related to inositol depletion in the PI cycle. Hypon atremia can lower brain inositol and hypernatremia can raise brain ino sitol. We now report that induction of low brain inositol by hyponatre mia followed by pilocarpine did not cause limbic seizures. Induction o f high brain inositol using hypernatremia followed by Li-pilocarpine a dministration did not reverse limbic seizures. These data support the concept that inositol available for PI synthesis and inositol for osmo tic function are sequestered in different cellular pools.