Duarte C B, Santos P F, Carvalho A P
Center for Neuroscience of Coimbra, Department of Zoology, University of Coimbra, Coimbra, Portugal.
J Neurosci Res. 1999 Nov 15;58(4):475-9. doi: 10.1002/(sici)1097-4547(19991115)58:4<475::aid-jnr1>3.0.co;2-o.
The Dale's law postulates that a neuron releases the same neurotransmitter from all its branches. In the case of multiple neurotransmitters it would require all transmitters to be released from all branches. The retinal cholinergic amacrine cells contain and release gamma-aminobutyric (GABA) and, therefore, if GABA and acetylcholine (ACh) are released at the same sites, this could mean that amacrine cells simultaneously excite and inhibit postsynaptic cells. Conversely, if the two neurotransmitters are released at different synapses, or if their release is regulated in a distinct manner, they may play different physiological roles. Recent studies carried out in cultured cholinergic amacrine-like neurons showed that Ca(2+)-dependent release of ACh and GABA have a different sensitivity to membrane depolarization, to the effect of blockers of voltage gated Ca(2+) channels (VGCC) and to the effect of presynaptic A(1) adenosine receptors. Therefore, it is proposed that in retinal amacrine cells the Ca(2+)-dependent release of ACh and GABA occurs at distinct cellular locations. The possible nature of these release sites and the physiological significance of this model are discussed in this review.
戴尔定律假定，一个神经元从其所有分支释放相同的神经递质。对于多种神经递质而言，这就要求所有递质都从所有分支释放。视网膜胆碱能无长突细胞含有并释放γ-氨基丁酸（GABA），因此，如果GABA和乙酰胆碱（ACh）在相同位点释放，这可能意味着无长突细胞同时兴奋和抑制突触后细胞。相反，如果这两种神经递质在不同突触释放，或者它们的释放以不同方式受到调节，那么它们可能发挥不同的生理作用。最近在培养的胆碱能无长突样神经元中进行的研究表明，ACh和GABA的钙依赖性释放对膜去极化、电压门控钙通道（VGCC）阻滞剂的作用以及突触前A(1)腺苷受体的作用具有不同的敏感性。因此，有人提出，在视网膜无长突细胞中，ACh和GABA的钙依赖性释放发生在不同的细胞位置。本文综述讨论了这些释放位点的可能性质以及该模型的生理意义。
