A possible alpha 2-adrenergic component in the in vivo activity of pirenperone.

The study used the loss of the righting reflex in response to the alpha 2-agonist xylazine in an in vivo rat assay to determine possible effects of the LSD antagonist pirenperone at alpha 2-adrenoceptors. Pirenperone antagonized the response and was more potent (ED50: 0.32 mg/kg) than yohimbine (1.25 mg/kg) and piperoxan (3.30 mg/kg). The data suggest that pirenperone may act at alpha 2-adrenoceptors in vivo.