Vizi E S, Tóth I E, Orsó E, Szalay K S, Szabó D, Baranyi M, Vinson G P
Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest.
J Endocrinol. 1993 Nov;139(2):213-26. doi: 10.1677/joe.0.1390213.
The effect of supramaximal electric field stimulation on [3H]dopamine (DA) release by rat adrenal capsule-glomerulosa preparations was studied using a micro-volume perfusion system. When the tissues were preloaded with [3H]DA, a considerable amount of [3H]DA and [3H]noradrenaline (NA) were released in response to field stimuli. Reserpinization, calcium removal or tetrodotoxin blocking of Na+ influx all completely inhibited the stimulation-evoked release of DA/NA, indicating that the radioactivity released is of neuronal and vesicular origin. In the adrenal cortex, a substantial proportion of tyrosine hydroxylase and dopamine-beta-hydroxylase immunoreactive nerve fibres and varicosities were observed around the zona glomerulosa. DA-containing nerves were not seen in the adrenal cortex; however, the same immunocytochemical procedures clearly demonstrated dopaminergic nerve cells and fibres in the substantia nigra and the striatum respectively, and cells of the adrenal medulla. Like the NA release from noradrenergic varicosities in the zona glomerulosa, the DA release from noradrenergic endings is not subject to negative feedback modulation through DA2 receptors since apomorphine, a DA2-receptor agonist, and sulpiride, a selective DA2-receptor antagonist, failed to affect the release. After in-vivo i.v. administration of [3H]DA, the glomerulosa content of DA and NA and the in-vitro release of [3H]DA and [3H]NA of zona glomerulosa both increased, indicating that the local varicose axon terminals were able to accumulate DA from the circulation, convert it into NA and release it in response to neural activity. This local arrangement of noradrenergic axon terminals, able to take up DA from the circulation and release it or convert it into NA, provides the possibility of a fine tuning of local circulation and aldosterone synthesis in the zona glomerulosa.
采用微量灌注系统研究了超强电场刺激对大鼠肾上腺被膜 - 球状带制剂释放[3H]多巴胺（DA）的影响。当组织预先加载[3H]DA时，响应电场刺激会释放出大量的[3H]DA和[3H]去甲肾上腺素（NA）。利血平化、去除钙或用河豚毒素阻断Na +内流均完全抑制了刺激诱发的DA/NA释放，表明释放的放射性物质来源于神经元和囊泡。在肾上腺皮质中，在球状带周围观察到相当比例的酪氨酸羟化酶和多巴胺 - β - 羟化酶免疫反应性神经纤维和曲张体。在肾上腺皮质中未见含DA的神经；然而，相同的免疫细胞化学方法分别清楚地显示了黑质和纹状体中的多巴胺能神经细胞和纤维以及肾上腺髓质的细胞。与球状带中去甲肾上腺素能曲张体释放NA一样，去甲肾上腺素能末梢释放DA不受通过DA2受体的负反馈调节，因为DA2受体激动剂阿扑吗啡和选择性DA2受体拮抗剂舒必利均未能影响释放。体内静脉注射[3H]DA后，球状带中DA和NA的含量以及球状带中[3H]DA和[3H]NA的体外释放均增加，表明局部曲张轴突末梢能够从循环中积累DA，将其转化为NA并响应神经活动而释放。这种能够从循环中摄取DA并释放或转化为NA的去甲肾上腺素能轴突末梢的局部排列，为球状带中局部循环和醛固酮合成的精细调节提供了可能性。
