División de Investigación, Facultad de Medicina, Universidad Nacional Autónoma de México, Av. Universidad No. 3000, Ciudad Universitaria, 04510 D.F. México.
Synapse. 2011 Jun;65(6):497-504. doi: 10.1002/syn.20866. Epub 2010 Nov 9.
In our study we investigated the influence of dopamine (DA) on the caudal photoreceptor (CPR) in crayfish. Here we report the following: (a) the chromatographic determination of DA in the sixth abdominal ganglion (6th AG) shows a variation in the content during a 24-h cycle with the maximum value at dawn. (b) There are possibly dopaminergic neurons in the 6th AG with antityrosine hydroxylase antibodies. Immunopositive neurons (164) were located in the anterior and posterior regions of the 6th AG with the mean (± SE) diameter of their somata 23 ± 1 μm. In addition, there is immunopositive staining in axons, neuropilar fibers, and varicosities. (c) We also identified, using immunohistochemistry, 108 neurons in the sixth AG that contain dopamine D1-like receptors, with the mean (±SE) diameter of their somata 18 ± 1 μm. (d) We examined the exogenous action of DA on the electrical activity of the CPR in the isolated sixth AG by conventional extracellular-recording methods. This CPR displays spontaneous activity and phasic-tonic responses to light pulses. Topical application of dopamine to ganglia kept in the dark increased the spontaneous firing rate of the CPR, whereas the photoresponse of the CPR remained unchanged. The effect on the spontaneous activity is dose-dependent with an ED₅₀ of 33 μM, and is blocked by the dopamine D1-like antagonist SCH23390. These observations suggested that the DA is playing the role of a neurotransmitter or a neuromodulator of the CPR in the 6th AG in both species of crayfish, Procambarus clarkii and Cherax quadricarinatus.
在我们的研究中，我们调查了多巴胺（DA）对螯虾尾状光感受器（CPR）的影响。在这里，我们报告以下内容：（a）在第六腹神经节（6th AG）中 DA 的色谱测定显示出 24 小时周期内含量的变化，最大值出现在黎明。（b）第六 AG 中可能存在具有抗酪氨酸羟化酶抗体的多巴胺能神经元。免疫阳性神经元（164 个）位于第六 AG 的前区和后区，其体细胞的平均（± SE）直径为 23 ± 1 μm。此外，在轴突、神经纤维和神经末梢中也有免疫阳性染色。（c）我们还使用免疫组织化学鉴定了第六 AG 中的 108 个神经元，这些神经元含有多巴胺 D1 样受体，其体细胞的平均（± SE）直径为 18 ± 1 μm。（d）我们通过常规的细胞外记录方法研究了 DA 对分离的第六 AG 中 CPR 电活动的外源性作用。这种 CPR 显示出自发活动和对光脉冲的相位-紧张反应。将多巴胺局部应用于在黑暗中保存的神经节增加了 CPR 的自发放电率，而 CPR 的光反应保持不变。该作用对自发活动具有剂量依赖性，ED₅₀为 33 μM，可被多巴胺 D1 样拮抗剂 SCH23390 阻断。这些观察结果表明，在两种螯虾（Procambarus clarkii 和 Cherax quadricarinatus）的第六 AG 中，DA 作为 CPR 的神经递质或神经调质发挥作用。
