(R)-(-)-α-Methylhistamine dihydrobromide

(R)-(-)-α-Methylhistamine dihydrobromide is a potent and selective H3 histamine receptor agonist with a Kd of 50.3 nM[1][2]. (R)-(-)-α-Methylhistamine dihydrobromide can cross the blood-brain barrier, and can enhance memory retention, attenuates memory impairment in rats[3][4][5].

Signaling Pathways >> Immunology/Inflammation >> Histamine Receptor

Research Areas >> Neurological Disease

Signaling Pathways >> GPCR/G Protein >> Histamine Receptor

H3 Receptor:50.3 nM (Kd)

(R)-(-)-α-Methylhistamine dihydrobromide is an H3-agonist that is > 10 times as potent as histamine (HA). Its selectivity toward H3-receptors is > 1,000 times as high as that of HA. (R)-(-)-α-Methylhistamine dihydrobromide has only weak affinities for H1 and H2 receptor with a pKi=4.8 and < 3.5, repectively. (R)-(-)-α-Methylhistamine dihydrobromide displays >200-fold selectivity over H4 receptors[1][2][3].

Pretreatment with (R)-(-)-α-Methylhistamine dihydrobromide (RAMH; 10 mg/kg; i.p.; 60 min before training) reverses propofol‐induced (25 mg/kg; i.p.; 30 min before training) memory retention[5]. (R)-alpha-Methylhistamine dihydrochloride (6.3 mg/kg; i.p.) significantly decreases the steady-state t-MH level in the mouse brain, whereas these compounds produced no significant changes in the HA level[3]. Animal Model: Male Sprague‐Dawley rats (10-12 week)[3] Dosage: 10 mg/kg Administration: IP; 60 min before training Result: Reversed propofol‐induced memory retention.

[1]. Arrang JM, et al. Highly potent and selective ligands for histamine H3-receptors. Nature. 1987 May 14-20;327(6118):117-23.

[2]. Mohammad Shahid, et al. Histamine, Histamine Receptors, and their Role in Immunomodulation: An Updated Systematic Review. The Open Immunology Journal, 2009, 2, 9-41.

[3]. Oishi R, et al. Effects of the histamine H3-agonist (R)-alpha-methylhistamine and the antagonist thioperamideon histamine metabolism in the mouse and rat brain. J Neurochem. 1989 May;52(5):1388-92.

[4]. Yamasaki S, et al. The disposition of (R)-alpha-methylhistamine, a histamine H3-receptor agonist, in rats. J Pharm Pharmacol. 1994 May;46(5):371-4.

[5]. Li WW, et al. (R)-alpha-methylhistamine suppresses inhibitory neurotransmission in hippocampal CA1 pyramidal neurons counteracting propofol-induced amnesia in rats. CNS Neurosci Ther. 2014 Sep;20(9):851-9.