The present investigation examined the interaction between fluoxetine
enantiomers and LSD in rats trained with LSD as a discriminative stimu
lus. The dose response relationships for LSD alone and in combination
with either (+)- or (-)-fluoxetine were determined. In both instances,
the LSD dose response relationship was shifted to the left. However,
statistical significance was observed only for the (+)-enantiomer. It
is concluded that the effects of LSD as a discriminative stimulus are
potentiated by the acute administration of fluoxetine. These results a
re consistent with anecdotal reports of interactions between LSD and a
cutely administered SSRIs in humans.