LSD’s effects are differentially modulated in arrestin knockout mice

ABSTRACT Recent evidence suggests that psychedelic drugs can exert beneficial effects on anxiety, depression, and ethanol and nicotine abuse in humans. However, the hallucinogenic side-effects of psychedelics often preclude their clinical use. Lysergic acid diethylamide (LSD) is a prototypical hallucinogen and its psychedelic actions are exerted through the 5-HT2A serotonin receptor (5-HT2AR). 5-HT2AR activation stimulates Gq- and β-arrestin-(βArr) mediated signaling. To separate effects of these signaling modes, we have used βArr1 and βArr2 mice. We find that LSD stimulates motor activities to similar extents in WT and βArr1-KO mice, with non-significant effects in βArr2-KOs. LSD robustly stimulates many surrogates of psychedelic drug actions including head twitches, grooming, retrograde walking, and nose poking in WT and βArr1-KO animals. In contrast, LSD only slightly stimulates head twitches in βArr2-KO mice, without effects on retrograde walking or nose poking. The 5-HT2AR antagonist MDL100907 (MDL) blocks these LSD effects. LSD also disrupts prepulse inhibition (PPI) in WT and βArr1-KOs; PPI is unaffected in βArr2-KOs. MDL restores PPI in WT mice, but this antagonist is without effect and haloperidol is required in βArr1-KOs. LSD produces a biphasic body-temperature response in WT mice, a monophasic response in βArr1-KOs, and is without effect in βArr2 mutants. Both MDL and the 5-HT1AR antagonist, WAY 100635 (WAY), block the effects of LSD on body temperatures in WT mice, whereas WAY is effective in βArr1-KOs. Collectively, these results reveal that LSD produces diverse behavioral effects through βArr1 and βArr2, and that LSD’s psychedelic drug-like actions appear to require βArr2.