A GABAergic Influence on the Light‐Induced Increase in Dopamine Turnover in the Dark‐Adapted Rat Retina In Vivo
A GABAergic Influence on the Light‐Induced Increase in Dopamine Turnover in the Dark‐Adapted Rat Retina In Vivo
复制标题
GABA 能对暗适应大鼠体内光诱导多巴胺周转增加的影响
作者：
W. W. Morgan;C. Kamp
翻译后摘要：光刺激酪氨酸羟化酶活性和多巴胺（DA）营业额在黑暗中适应大鼠视网膜在体内。DA神经元位于无长突细胞层，并与该层中的其他细胞形成许多连接。可以想象，这些其他细胞中神经传递的改变可能会影响DA神经元的光反应参数。本文提供的证据表明，GABA系统的体内药理学操作可改变光诱导的DA周转率变化。α-甲基-对-酪氨酸（αMPT，250 mg/kg，i. p.）用于估计DA营业额。光照30或60分钟显著增强了μMPT处理大鼠视网膜中DA含量的下降。两种剂量的强效GABA激动剂蝇蕈醇（13.2或26.4 μmol/kg，静脉注射，累积）显著抑制光诱导的DA周转增加（p <.001）。这种作用对GABA是选择性的，因为GABA拮抗剂苦毒宁（1.88 mg/kg，i. v.，累积）逆转蝇蕈醇介导的光诱导刺激的阻断。事实上，DA营业额的存在下，光，蝇蕈醇和苦毒素是没有不同的DA营业额在光单独。这些数据表明，有一个直接或间接的GABA能输入到大鼠视网膜的DA系统。目前的研究旨在澄清生理作用，如果有的话，这种输入在视网膜DA系统的正常光响应中起作用。
Abstract: Light stimulates tyrosine hydroxylase activity and dopamine (DA) turnover in the dark‐adapted rat retina in vivo. The DA neurons are located in the amacrine cell layer and form numerous connections with other cells in this layer. Conceivably, alterations in neurotransmission in these other cells could influence the light‐responding parameters of the DA neurons. Evidence presented in this paper shows that in vivo pharmacologic manipulation of the GABA system modifies the light‐induced change in DA turnover. The decline in DA content following inhibition of tyrosine hydroxylase by α‐methyl‐p‐tyrosine (αMPT, 250 mg/kg, i.p.) was used to estimate DA turnover. The decline in DA content in retinas of the μMPT‐treated rats was significantly enhanced by light exposure for 30 or 60 min. Two doses of the potent GABA agonist muscimol (13.2 or 26.4 μmol/kg, i.v., cumulative) significantly inhibited the light‐induced increase in DA turnover (p <.001). This action was selective for GABA because the GABA antagonist picrotoxinin (1.88 mg/kg, i.v., cumulative) reversed the muscimol‐mediated blockade of the light‐induced stimulation. In fact, DA turnover in the presence of light, muscimol, and picrotoxinin was not different from DA turnover in light alone. These data suggest that there is either a direct or indirect GABAergic input to the DA system of the rat retina. Current studies are aimed at clarifying the physiological role, if any, that this input plays in the normal light response of the retinal DA system.