Purity >98%. Rauwolscine is a natural alkaloid that acts as a selective and reversible Alpha2 -adrenergic receptor antagonist (Ki = 12 nM). It is a stereoisomer of yohimbine, which potently antagonizes both Alpha1 - and Alpha2 -adrenergic receptors. Rauwolscine also acts as a receptor antagonist at the serotonin 5-HT2B receptor (Ki = 14.3 nM) and as a weak partial agonist at 5-HT1A (IC50 = 1.3 μM). The Alpha2 -adrenergic receptor has diverse physiological functions and antagonists like rauwolscine have numerous applications, including the modulation of mood and behavior.