Wang Y, Okamura T, Toda N
Department of Pharmacology, Shiga University of Medical Sciences, Ohtsu, Japan.
Invest Ophthalmol Vis Sci. 1993 Jan;34(1):41-8.
Mechanisms that underlie the relaxant response to histamine were examined in dog external (a branch of external carotid artery) and internal (a branch of internal carotid artery) ophthalmic arteries (EOA and IOA).
Changes in isometric tensions were recorded in helical strips of the arteries with and without the endothelium.
Histamine predominantly produced relaxations in EOA and IOA, partially contracted with prostaglandin (PG) F2 alpha. The relaxation of IOA almost was abolished by treatment with cimetidine (10(-5) mol/l), whereas the response of EOA was partially attenuated by treatment with cimetidine or chlorpheniramine (10(-6) mol/l) and was abolished with their combined treatment. Endothelium denudation depressed the relaxation in EOA but did not affect the response of IOA. The response to histamine of EOA was inhibited by treatment with indomethacin (10(-6) mol/l) or tranylcypromine (10(-4) mol/l), a PGI2 synthesis inhibitor, only when the endothelium was present, but additional treatment with chlorpheniramine did not further inhibit relaxation. On the other hand, IOA's response to histamine was not inhibited by indomethacin, despite the presence of endothelium.
The histamine-induced relaxation in EOA may be associated with the release of vasodilator PGI2 through the activation of H1 receptors in the endothelium and with the direct action on H2 receptors in smooth muscle, whereas the relaxation in IOA is mediated exclusively by H2 receptors in smooth muscle.
研究组胺对犬眼外动脉（颈外动脉分支）和眼内动脉（颈内动脉分支）的舒张反应机制。
记录有内皮和无内皮动脉螺旋条的等长张力变化。
组胺主要使眼外动脉和眼内动脉舒张，用前列腺素（PG）F2α预收缩后再给予组胺。西咪替丁（10⁻⁵mol/L）处理几乎完全消除眼内动脉的舒张反应，而眼外动脉的反应经西咪替丁或氯苯那敏（10⁻⁶mol/L）处理后部分减弱，联合处理则完全消除。去除内皮可抑制眼外动脉的舒张反应，但不影响眼内动脉的反应。仅在内皮完整时，吲哚美辛（10⁻⁶mol/L）或PGI2合成抑制剂反苯环丙胺（10⁻⁴mol/L）处理可抑制眼外动脉对组胺的反应，但氯苯那敏进一步处理并不增强抑制作用。另一方面，尽管存在内皮，吲哚美辛并不抑制眼内动脉对组胺的反应。
组胺诱导的眼外动脉舒张可能与通过激活内皮H1受体释放血管舒张性PGI2以及直接作用于平滑肌H2受体有关，而眼内动脉的舒张仅由平滑肌H2受体介导。
