Effect of lithium on synaptosomal brain enzymes.

During 7 days of lithium administration to rats, the levels of adenylate cyclase bound to brain synaptosomes decreased, while those of acetylcholinesterase increased. Both enzyme levels returned to their initial values after 1 month of treatment. Monoamine oxidase, which is bound to a mitochondrial membrane, was not affected by lithium treatment. Arrhenius plots of the brain synaptosomal enzymes (Na + K)ATPase and acetylcholinesterase from rats treated with LiCl for 7 or 30 days showed a lower transition temperature. Also, when these synaptosomal enzymes were exposed to such exogenous agents as detergents or alcohol, the reaction of the enzymes obtained from lithium treated rats was different than that of control rats. These effects disappeared after ceasing lithium administration for one week. These data indicate changes in the structure of brain membranes after lithium administration.