LSD as an agonist at mesolimbic dopamine receptors

The dopamine agonist apomorphine (1.0 mg/kg i.p.) produced an enhanced stimulation of locomotor activity compared to control animals in rats injected bilaterally 14 days previously with 6-hydroxydopamine (6OHDA) into the nucleus accumbens. (+)-Lysergic acid diethylamide (LSD) also produced a marked stimulation of locomotor activity in the 6OHDA treated animals at a dose (1.0 mg/kg i.p.) which was ineffective in control rats. (+)-Bromo-lysergic acid diethylamide (2.0 mg/kg i.p.) did not stimulate locomotor activity in 6OHDA treated rats. The locomotor stimulation produced by LSD was blocked by pretreatment with the dopamine antagonist pimozide (0.5 mg/kg i.p.). It is suggested that LSD acts as an agonist at mesolimbic dopamine receptors.