Poelchen W, Sieler D, Wirkner K, Illes P
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Härtelstrasse 16-18, D-04107, Leipzig, Germany.
Neuroscience. 2001;102(3):593-602. doi: 10.1016/s0306-4522(00)00529-7.
Intracellular recordings were made in a mid-pontine slice preparation of the rat brain containing the nucleus locus coeruleus. Focal electrical stimulation evoked biphasic synaptic potentials consisting of early depolarizing (d.p.s.p.) and late hyperpolarizing (i.p.s.p.) components. The alpha(2)-adrenoceptor antagonist idazoxan inhibited the i.p.s.p. without altering the d.p.s.p. All of the following experiments were carried out in the presence of kynurenic acid and picrotoxin to block the glutamatergic and GABAergic fractions of the d.p.s.p., respectively. Guanethidine, which is known to inhibit noradrenaline and ATP release from nerve terminals of postganglionic sympathetic nerves, depressed both the d.p.s.p. and the i.p.s.p. in a concentration-dependent manner. Damage of catecholaminergic nerve terminals by 6-hydroxydopamine also decreased both the d.p.s.p. and the i.p.s.p. The P2 receptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) depressed the d.p.s.p., whereas the i.p.s.p. remained unaffected. The further application of PPADS did not increase the depression of the d.p.s.p. by guanethidine. Superfusion with the mixed alpha-adrenoceptor agonist noradrenaline or the selective P2 receptor agonist adenosine 5'-O-(2-thiodiphosphate) inhibited both the d.p.s.p. and the i.p.s.p. The inhibitory effects of these agonists were prevented by the respective antagonists idazoxan or suramin. In the presence of suramin noradrenaline failed to inhibit the residual d.p.s.p. Superfused noradrenaline potentiated rather than inhibited responses to pressure-applied alpha,beta-methylene-ATP; superfused adenosine 5'-O-(2-thiodiphosphate) did not interact with pressure-applied noradrenaline. In conclusion, we present electrophysiological evidence for the co-release of ATP and catecholamines in the CNS. At the cell somata of neurons in the locus coeruleus, noradrenaline and ATP activate inhibitory alpha(2)-adrenoceptors and excitatory P2 receptors, respectively. In addition, inhibitory presynaptic autoreceptors of the alpha(2) and P2 types appear to regulate release of the two co-transmitters.
在包含蓝斑核的大鼠脑桥中部脑片标本上进行细胞内记录。局灶性电刺激诱发双相突触电位，由早期去极化（d.p.s.p.）和晚期超极化（i.p.s.p.）成分组成。α₂肾上腺素能受体拮抗剂咪唑克生抑制i.p.s.p.，而不改变d.p.s.p.。以下所有实验均在犬尿氨酸和印防己毒素存在的情况下进行，以分别阻断d.p.s.p.的谷氨酸能和GABA能成分。已知可抑制节后交感神经神经末梢去甲肾上腺素和ATP释放的胍乙啶，以浓度依赖性方式抑制d.p.s.p.和i.p.s.p.。6-羟基多巴胺对儿茶酚胺能神经末梢的损伤也降低了d.p.s.p.和i.p.s.p.。P2受体拮抗剂磷酸吡哆醛-6-偶氮苯基-2',4'-二磺酸（PPADS）抑制d.p.s.p.，而i.p.s.p.不受影响。进一步应用PPADS并未增加胍乙啶对d.p.s.p.的抑制作用。用混合α肾上腺素能激动剂去甲肾上腺素或选择性P2受体激动剂腺苷5'-O-（2-硫代二磷酸）灌流可抑制d.p.s.p.和i.p.s.p.。这些激动剂的抑制作用可被各自的拮抗剂咪唑克生或苏拉明阻断。在苏拉明存在的情况下，去甲肾上腺素未能抑制残余的d.p.s.p.。灌流的去甲肾上腺素增强而非抑制对压力施加的α,β-亚甲基-ATP的反应；灌流的腺苷5'-O-（2-硫代二磷酸）与压力施加的去甲肾上腺素不相互作用。总之，我们提供了中枢神经系统中ATP和儿茶酚胺共同释放的电生理证据。在蓝斑核神经元的细胞体上,去甲肾上腺素和ATP分别激活抑制性α₂肾上腺素能受体和兴奋性P2受体。此外，α₂和P2型抑制性突触前自身受体似乎调节这两种共递质的释放。
