Background:

Phenoxybenzamine hydrochloride is a selective antagonist of both α-adrenoceptor and calmodulin that is commonly used for the treatment of hypertension, specifically caused by pheochromocytoma.
The IC50 (100 nM) derived from the blockade of [3H]yohimbine binding by Phenoxybenzamine hydrochloride is significantly less than the IC50 (550 nM) for the corresponding reversal by Phenoxybenzamine hydrochloride of the effects of norepinephrine on cyclic AMP accumulation[1]. Phenoxybenzamine hydrochloride (50 nM) in conbination with Phenoxybenzamine hydrochloridetolamine (1000 nM) enhances Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with pretreatment with Phenoxybenzamine hydrochloride (50 nM) alone in endothelium-intact aortae. Combined treatment with either dexmedetomidine (300 or 1000 nM) and Phenoxybenzamine hydrochloride (50 nM) or Phenoxybenzamine hydrochloridetolamine (1000 nM) and Phenoxybenzamine hydrochloride (50 nM) enhance Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with Phenoxybenzamine hydrochloride alone (50 nM). In addition, combined treatment with Phenoxybenzamine hydrochloridetolamine and Phenoxybenzamine hydrochloride enhances Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with dexmedetomidine (1000 nM) and Phenoxybenzamine hydrochloride combined treatment. Combined treatment with high concentrations of dexmedetomidine (1000 nM) and Phenoxybenzamine hydrochloride enhances Phenoxybenzamine hydrochlorideylephrine-induced contraction compared with combined treatment with low concentrations of dexmedetomidine (300 nM) and Phenoxybenzamine hydrochloride[2]. Phenoxybenzamine hydrochloride (0.1-100 μM) inhibits glioma proliferation, migration, and invasion and suppresses the tumorigenesis capacity. Phenoxybenzamine hydrochloride also inhibits self-renewal of glioma stem-like cells. Phenoxybenzamine hydrochloride activates LINGO-1 and inhibits the TrkB-Akt pathway[3]. Phenoxybenzamine hydrochloride (0.1 μM-1 mM) preserves primary neurons within the CA1, CA3 and dentate gyrus and produces a robust neuroprotective effect, and prevents neuronal death from OGD in all regions of the hippocampus when delivered at 2, 4, and 8 h post-OGD at 100 μM[4].
Phenoxybenzamine hydrochloride (20 nM, s.c.) effectively suppresses the tumorigenesis of glioma cells in mice and the cell density in Phenoxybenzamine hydrochloride-U87MG xenografts decreases significantly[3]. Phenoxybenzamine hydrochloride (1 mg/kg, i.v.) treated rats shows significant improvements in NSS and foot fault scoring[4].
Reference:
[1]. Lenox, R.H., et al, Alpha 2-adrenergic receptor-mediated regulation of adenylate cyclase in the intact human platelet. Evidence for a receptor reserve. Mol Pharmacol, 1985. 27(1): p. 1-9.
[2]. Byon HJ, et al. Dexmedetomidine Inhibits Phenylephrine-induced Contractions via Alpha-1 Adrenoceptor Blockade and Nitric Oxide Release in Isolated Rat Aortae. Int J Med Sci. 2017 Feb 7;14(2):143-149.
[3]. Lin XB, et al. Anti-tumor activity of phenoxybenzamine hydrochloride on malignant glioma cells. Tumour Biol. 2016 Mar;37(3):2901-8.
[4]. Rau TF, et al. Phenoxybenzamine is neuroprotective in a rat model of severe traumatic brain injury. Int J Mol Sci. 2014 Jan 20;15(1):1402-17.