Further studies on the potentiating effect of lithium chloride on methamphetamine-induced stereotypy in mice

To study the mechanism of the potentiating effect of lithium chloride (LiCl) on methamphetamine (MA)-induced stereotypy in mice, effects of various drugs on the action of LiCl on the stereotypy and pharmacokinetics of MA in different brain regions and liver were examined. The potentiating effect of LiCl disappeared in mice pretreated with atropine or scopolamine whereas LiCl potentiated the stereotypy in mice pretreated with p-chlorophenylalanine, alpha-methyl-p-tyrosine, nialamide, physostigmine or butylscopolamine. The concentrations of MA in the striatum, brainstem and liver were increased and the half-life of MA in these tissues was prolonged by LiCl. The effect of LiCl on the kinetics of MA in the brain, but not that in the liver, was blocked by scopolamine. LiCl prolonged the half-life of MA in the brain and liver in mice treated with physostigmine or butylscopolamine. The inhibition of MA elimination from the brain and its blockade by scopolamine seem to explain the potentiating action of LiCl on the stereotypy and the antagonism by scopolamine of the behavioural action of LiCl, respectively.