Saifullah A S M, Tomioka Kenji
Yamaguchi University, Research Institute for Time Studies, Department of Physics, Biology and Informatics, Faculty of Science, Yamaguchi 753-8512, Japan.
J Insect Physiol. 2003 Mar;49(3):231-9. doi: 10.1016/s0022-1910(02)00270-6.
Pigment-dispersing factor (PDF) is an octadeca-neuropeptide widely distributed in the insect brain and suggested to be involved in the insect circadian systems. We have examined its effects on the neuronal activity of the brain efferents in the optic stalk including medulla bilateral neurons (MBNs) in the cricket, Gryllus bimaculatus. The MBNs are visually responding interneurons connecting the bilateral medulla, which show a clear day/night change in their light responsiveness that is greater during the night. Microinjection of PDF into the optic lobe induced a significant increase in the spontaneous activity of the brain efferents and the photo-responsiveness of the MBNs during the day, while little change was induced during the night. The enhancing effects began to occur about 20 min after the injection and another 10 min was necessary to reach the maximal level. The effects of PDF were dose-dependent. When 22 nl of anti-Gryllus-PDF (1:200) IgG was injected into the medulla, the photo-responsiveness of the MBNs was suppressed in both the day and the night with greater magnitude during the night. No significant suppression was induced by injection of the same amount of IgG from normal rabbit serum. These results suggest that in the cricket optic lobe, PDF is released during the night and enhances MBNs' photo-responsiveness to set their night state.
色素分散因子（PDF）是一种十八肽神经肽，广泛分布于昆虫大脑中，被认为参与昆虫的昼夜节律系统。我们研究了其对双斑蟋视柄中脑传出神经元活动的影响，这些神经元包括髓质双侧神经元（MBNs）。MBNs是连接双侧髓质的视觉反应中间神经元，它们的光反应性在白天和黑夜有明显变化，夜间更强。向视叶微量注射PDF会导致白天脑传出神经元的自发活动以及MBNs的光反应性显著增加，而夜间几乎没有变化。增强作用在注射后约20分钟开始出现，再过10分钟达到最大水平。PDF的作用呈剂量依赖性。当向髓质注射22 nl抗双斑蟋-PDF（1:200）IgG时，MBNs的光反应性在白天和黑夜均受到抑制，夜间抑制程度更大。注射相同量的正常兔血清IgG未引起明显抑制。这些结果表明，在双斑蟋视叶中，PDF在夜间释放，增强MBNs的光反应性以设定它们的夜间状态。
