Methoxamine as a tool to assess the importance of intraneuronal uptake of l-norepinephrine in the cat's nictitating membrane.
Methoxamine as a tool to assess the importance of intraneuronal uptake of l-norepinephrine in the cat's nictitating membrane.
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甲氧明作为评估猫瞬膜神经元内摄取 L-去甲肾上腺素重要性的工具。
DOI：
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发表时间：
1970
影响因子：
3.5
通讯作者：
S. Pluchino
中科院分区：
文献类型：
--
作者：
U. Trendelenburg;R. Maxwell;S. Pluchino
将分离的兔主动脉条暴露于甲氧胺-H3。在导致去甲肾上腺素-H3大量保留的条件下，其保留可以忽略不计。由于甲氧胺的神经元内摄取似乎非常小，因此使用该胺来测试由以下概念产生的各种假设：在猫的瞬膜中，神经元内摄取是影响受体处 L-去甲肾上腺素浓度的最重要因素。甲氧胺对瞬膜有直接作用。与假设一致，在已知对 L-去甲肾上腺素产生明显超敏反应的实验条件下，可卡因或去神经支配未能引起对甲氧明的超敏反应。另一方面，两种胺的分散超敏感性同样明显。这一观察结果支持了以下观点：去中心化超敏感性是由突触后事件引起的。在正常和去神经的离体瞬膜上，酚妥拉明与甲氧明的拮抗作用是竞争性的。另一方面，早期的观察表明，当神经元内摄取机制完整时，酚妥拉明与 L-去甲肾上腺素的拮抗作用似乎不具有竞争性。结果支持这样的观点：在猫的瞬膜中，神经元内的摄取对受体处去甲肾上腺素的浓度具有决定性影响。慢性去中心化或慢性去神经支配导致甲氧明剂量反应曲线斜率下降；显然，摄取饱和度并不是拟交感胺剂量反应曲线斜率的唯一决定因素。
Isolated rabbit aortic strips were exposed to methoxamine-H3. Its retention was negligible under conditions which led to considerable retention of norepinephrine-H3. Since intraneuronal uptake of methoxamine seems to be very small, the amine was used to test various postulates arising out of the concept that, in the nictitating membrane of the cat, intraneuronal uptake is the most important factor influencing the concentration of l -norepinephrine at the receptors. On the nictitating membrane, methoxamine has a direct effect. In agreement with postulates, cocaine or denervation failed to cause supersensitivity to methoxamine under experimental conditions which are known to produce pronounced supersensitivity to l -norepinephrine. Decentralization supersensitivity, on the other hand, was equally pronounced for both amines; this observation supports the view that decentralization supersensitivity is due to a postsynaptic event. On the normal and on the denervated isolated nictitating membrane the antagonism of phentolamine to methoxamine was of the competitive type. Earlier observations, on the other hand, had shown that the antagonism of phentolamine to l -norepinephrine appeared not to be competitive when the intraneuronal uptake mechanism was intact. The results support the view that, in the cat's nictitating membrane, intraneuronal uptake has a decisive influence on the concentration of norepinephrine at the receptors. Chronic decentralization or chronic denervation caused a decrease in the slopes of dose-response curves for methoxamine; apparently, saturation of uptake is not the only determinant of slopes of dose response curves for sympathomimetic amines.