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1 Carcinine (beta-alanyl histamine) is an imidazole dipeptide. The present study was designedto characterize the pharmacological effects of carcinine on histaminergic activity in the brain andon certain neurobehavior.2 Carcinine was highly selective for the histamine Ha receptor over H1 or H2 receptor [Ki (μM)= 0.2939 ± 0.2188 vs. 3621.2 ± 583.9 or 365.3 ± 232.8 μM, respectively].3 Carcinine, at a dose of 20 mg kg-1 slightly increased histidine decarboxylase (HDC) activity inthe cortex (from 0.186 ± 0.069 pmol mg protein-1 min-1 to 0.227 ± 0.009 pmol mg protein-1 min-1).In addition, carcinine (10, 20 and 50 mg kg-1) significantly decreased histamine levels in micebrain.4 Like thioperamide, a histamine H3 receptor antagonist, carcinine (20, 50 μM) significantlyincreased 5-HT release from mice cortex slices, but had no apparent effect on dopamine release.5 Carcinine (20 mg kg-1) significantly inhibited pentylenetetrazole- induced kindling. Thisinhibition was completedly reversed by (R)-α-methylhistamine, a representative H3 receptoragonist, and α-fluromethylhistidine, a selective histidine decarboxylase inhibitor.6 The results of this study provide first and direct evidence that carcinine, as a novel histamineH3 receptor antagonist, plays an important role in histaminergic neurons activation and might beuseful in the treatment of certain diseases, such as epilepsy.