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Shinichi Otani, Taiji Nagaoka, Tsuneaki Omae, Shinji Ono, Takayuki Kamiya, Akitoshi Yoshida; HISTAMINE ELICITS DILATION OF ISOLATED PORCINE RETINAL ARTERIOLES. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4346.
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Histamine is an autacoid and causes various reactions, such as allergies, neural transmission, gastric-acid secretion, bronchial contraction, and vessel dilatation. Recent studies have reported that plasma histamine concentrations are elevated in patients with diabetes mellitus, suggesting that histamine may contribute to the etiology of diabetic retinopathy. However, it is unknown if histamine has directly affects ocular microvascular reactivity. We examined the direct effect and the underlying mechanism of the vasomotor action of histamine in porcine retinal arterioles.
Porcine retinal arterioles (90-110 microns in internal diameter) were isolated, cannulated, and pressurized (55 cmH2O) without flow for this in vitro study. Videomicroscopic techniques were used to record the changes in diameter in the retinal arterioles in response to histamine.
The retinal arterioles dilated in a dose-dependent manner in response to histamine (0.1 n -0.1 mM). The nitric oxide (NO) synthase inhibitor N-nitro-L-arginine methyl ester (10 microns) inhibited the effect of histamine-induced vasodilation (p=0.01).
The current findings suggested that histamine-induced vasodilation is mediated by the released NO in the retinal arterioles.
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