Rörig B, Klausa G, Sutor B
Department of Physiology, University of Munich, Germany.
J Neurosci. 1995 Nov;15(11):7386-400. doi: 10.1523/JNEUROSCI.15-11-07386.1995.
During early postnatal development, lamina II/III pyramidal cells in rat neocortex are extensively coupled via gap junctions. The factors regulating gap junction permeability, as well as the mechanisms underlying the developmental uncoupling process are not understood. To investigate the influence of protein kinase A-mediated phosphorylation on dye coupling in the developing neocortex, pyramidal cells in slices of rat frontal and prefrontal cortex were injected intracellularly with the tracer neurobiotin. Control injections revealed clusters of about 30 dye-coupled neurons. Preincubation with forskolin or direct activation of protein kinase A with Sp-cAMPS reduced the number of coupled cells by about 70%. A significant reduction in dye coupling was also observed following incubation with dopamine. Application of receptor selective agonists and antagonists revealed that the uncoupling was mediated by both dopamine D1 and D2 receptors. The protein kinase A inhibitor Rp-cAMPS reduced the effect of dopamine, suggesting that the neurotransmitter regulates gap junction permeability via protein kinase A activation. In the presence of either forskolin, Sp-cAMPS, or dopamine, neurons displayed a significantly higher input resistance compared to control conditions. During the second postnatal week, transient application of forskolin to single neurons reversibly increased input resistance. At later developmental stages when coupling incidence had declined, this action of forskolin was no longer observed. Our data demonstrate a dependence of gap junction permeability on protein kinase A activity and on dopamine receptor activation in developing rat neocortical neurons. These mechanisms may modulate junctional permeability during the period of circuit formation.
在出生后早期发育阶段，大鼠新皮质中的II/III层锥体细胞通过缝隙连接广泛耦合。调节缝隙连接通透性的因素以及发育性解偶联过程的潜在机制尚不清楚。为了研究蛋白激酶A介导的磷酸化对发育中的新皮质染料耦合的影响，将示踪剂神经生物素细胞内注射到大鼠额叶和前额叶皮质切片中的锥体细胞中。对照注射显示约30个染料耦合神经元的簇。用福斯高林预孵育或用Sp-cAMPS直接激活蛋白激酶A可使耦合细胞数量减少约70%。用多巴胺孵育后也观察到染料耦合显著减少。应用受体选择性激动剂和拮抗剂表明，解偶联由多巴胺D1和D2受体介导。蛋白激酶A抑制剂Rp-cAMPS降低了多巴胺的作用，表明神经递质通过蛋白激酶A激活调节缝隙连接通透性。在存在福斯高林、Sp-cAMPS或多巴胺的情况下，与对照条件相比，神经元表现出显著更高的输入电阻。在出生后第二周，对单个神经元短暂应用福斯高林可逆地增加输入电阻。在发育后期，当耦合发生率下降时，不再观察到福斯高林的这种作用。我们的数据表明，缝隙连接通透性在发育中的大鼠新皮质神经元中依赖于蛋白激酶A活性和多巴胺受体激活。这些机制可能在回路形成期间调节连接通透性。
