Differential effects produced by Δ 1-tetrahydrocannabinol on lateral geniculate neurones

The active ingredient of marihuana, Δ 1-tetrahydrocannabinol, exerts a differential effect on lateral geniculate neurones in the rat. Units that fire when the eye is illuminated are inhibited by the drug, whereas those that discharge in the dark but are inhibited by light either remain unchanged or increase their rate of firing. This dual effect has also been observed on lateral geniculate field potentials. Preliminary results also suggest that these effects may be mediated by midbrain monoaminergic neurones.