Rauwolscine hydrochloride (Synonyms: Isoyohimbine, NSC 407307, αYohimbine)

Rauwolscine hydrochloride is a potent and specific α2 adrenergic receptor antagonist with a Ki of 12 nM.

[3H]Rauwolscine binding to α2 adrenergic receptor is reversible, stcreospccific, and saturable. [3H]Rauwolscine specifically labels both the high and low affinity states of the α2 adrenergic receptor in brain membranes[1]. [3H]Rauwolscine also behaves as a 5-HT1A receptor agonist and this conclusion is compatible with earlier functional studies, indicating that rauwolscine (as well as yohimbine) has agonistic properties at the level of 5-HT autoreceptors[2]. When using [3H]5-HT as a radioligand, rauwolscine is determined to have relatively high affinity for the human receptor (Ki human=14.3 nM, Ki rat=35.8 nM)[3]. Saturation studies shows that the affinity of [3H]Rauwolscine is similar in mouse, rat, rabbit, dog (2.33-3.03 nM) except man where it is significantly higher (0.98 nM) [4].

References:
[1]. Perry BD, et al. [3H]rauwolscine (alpha-yohimbine): a specific antagonist radioligand for brain alpha 2-adrenergic receptors. Eur J Pharmacol. 1981 Dec 17;76(4):461-4.
[2]. De Vos H, et al. [3H]rauwolscine behaves as an agonist for the 5-HT1A receptors in human frontal cortex membranes. Eur J Pharmacol. 1991 May 25;207(1):1-8.
[3]. Wainscott DB, et al. [3H]Rauwolscine: an antagonist radioligand for the cloned human 5-hydroxytryptamine2b (5-HT2B) receptor. Naunyn Schmiedebergs Arch Pharmacol. 1998 Jan;357(1):17-24.
[4]. Neylon CB, et al. [3H]-rauwolscine binding to alpha 2-adrenoceptors in the mammalian kidney: apparent receptor heterogeneity between species. Br J Pharmacol. 1985 Jun;85(2):349-59.