Hardie R C
Cambridge University, Department of Zoology, England, UK.
Nature. 1989 Jun 29;339(6227):704-6. doi: 10.1038/339704a0.
Compared with the variety of neuromodulatory agents acting through second messenger systems, the number of fast neurotransmitters which directly activate ion channels is limited. Thus, synaptic receptors that act as ligand-gated ion channels have been firmly established only for acetylcholine, glycine, GABA and glutamate, with the first three of these belonging to the same molecular superfamily. Recently, however, a possible addition to this list has been suggested as a result of evidence implicating histamine as the neurotransmitter released by a variety of arthropod photoreceptors. Neurotransmission at this synapse has been studied extensively, particularly in the fly. The postsynaptic elements, large monopolar cells, respond to light with a rapid, chloride-mediated hyperpolarization that can be mimicked by the application of histamine. In this report I document some basic properties of the histamine receptors present on large monopolar cells isolated from blowfly optic lobes. The receptor is a ligand-gated chloride channel showing properties consistent with its presumed role of mediating neurotransmission at the photoreceptor synapse.
与通过第二信使系统发挥作用的多种神经调节因子相比，直接激活离子通道的快速神经递质数量有限。因此，作为配体门控离子通道起作用的突触受体仅在乙酰胆碱、甘氨酸、γ-氨基丁酸（GABA）和谷氨酸中得到了明确证实，其中前三种属于同一分子超家族。然而，最近有证据表明组胺是多种节肢动物光感受器释放的神经递质，这可能使该列表有所增加。人们对这个突触的神经传递进行了广泛研究，尤其是在果蝇中。突触后元件，即大的单极细胞，对光的反应是快速的、氯离子介导的超极化，应用组胺也能模拟这种超极化。在本报告中，我记录了从丽蝇视叶分离出的大的单极细胞上组胺受体的一些基本特性。该受体是一种配体门控氯离子通道，其特性与其在光感受器突触介导神经传递的假定作用一致。
