Siggins G R
Adv Exp Med Biol. 1979;116:41-64. doi: 10.1007/978-1-4684-3503-0_3.
An effort has been made here to devise criteria allowing discrimination between neurotransmitters, modulators and mediators. However, after consideration of several technical pitfalls in studies of these criteria, and examination of the properties of two examples of neuroactive agents (norepinephrine and endorphins) often referred to as "modulators", it is still difficult to classify these agents in all cases. Thus, in most central targets where NE-fibers are known to terminate, the synaptic actions of NE appear to have properties of both a neuromodulator and a neurotransmitter. Although much more research needs to be pursued, the opioid peptides may be neuromodulators for some neurons (spinal cord neurons) and neurotransmitters for others (myenteric plexus and spinal cord neurons). It may be that classification of such peptide agonists will need to be done on a cell-by-cell basis, with the endogenous peptides subserving a multi-faceted role in central and peripheral neuronal communication. As more and more endogenous ligands and transmitter-like substances are extracted from brain, it begins to appear that the language of neuronal communication is much richer than originally imagined from responses of spinal neurons to the fast-acting classical neurotransmitters. Indeed, it may evolve that the "deviant" forms of communication or transmission are more the rule than the exception. In the final analysis, each neurotransmitter may possess its own "fingerprint" of holistic actions attesting to the unique individuality of neuron types and their neurotransmitters. Such individualities might be expected to accomplish more sophisticated integrative operations, and hence behaviors, than could simple rapid "yes" or "no" messages.
本文致力于制定区分神经递质、调质和介质的标准。然而，在考虑了这些标准研究中的几个技术陷阱，并研究了通常被称为“调质”的两种神经活性物质（去甲肾上腺素和内啡肽）的特性后，在所有情况下对这些物质进行分类仍然很困难。因此，在已知去甲肾上腺素纤维终止的大多数中枢靶点中，去甲肾上腺素的突触作用似乎同时具有神经调质和神经递质的特性。尽管还需要进行更多的研究，但阿片肽对某些神经元（脊髓神经元）可能是神经调质，而对另一些神经元（肌间神经丛和脊髓神经元）则是神经递质。可能需要逐细胞地对这类肽激动剂进行分类，内源性肽在中枢和外周神经元通讯中发挥着多方面的作用。随着越来越多的内源性配体和类似递质的物质从脑中提取出来，神经元通讯的语言似乎比最初从脊髓神经元对快速作用的经典神经递质的反应中想象的要丰富得多。事实上，可能会发现“异常”形式的通讯或传递更为常见而非例外。归根结底，每种神经递质可能都有其独特的整体作用“指纹”，这证明了神经元类型及其神经递质的独特个性。与简单快速的“是”或“否”信息相比，这些个性可能会完成更复杂的整合操作，进而产生更复杂的行为。
