Facilitating effects of histamine on spatial memory deficit induced by scopolamine in rats

AIM: To investigate whether or not histamine was involved in scopolamine-induced spatial memory deficits evaluated in 8-arm radial maze performance of rats. METHODS: Eight-Arm radial maze performance was used to measure spatial memory in rats, and the brain regions were subsequently dissected and histamine contents were determined by HPLC. RESULTS: Intracerebroventricular (icv) injection of histamine (100 or 200 ng) or thioperamide (50 mu g), and intraperitoneal tip) injection of histidine (1000 mg/kg) ameliorated memory impairment induced by scopolamine regarding both parameters of radial maze performance. 2-Thiazolylethylamine, but not 4-methylhistamine showed the similar effect to histamine. Both histamine (200 ng, icy) and histidine (1000 mg/kg, ip) were equally effective in increasing the histamine content in the cortex, hippocampus, and hypothalamus. CONCLUSION: These results suggest that brain histamine plays an important role in learning and memory, and its action may be due to cholinergic neurons.