Department of Biology, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA.
Gen Comp Endocrinol. 2010 Mar 1;166(1):54-65. doi: 10.1016/j.ygcen.2009.08.008. Epub 2009 Aug 21.
Ecdysis, or the shedding of the old cuticle, depends on coordinated stereotyped behaviors, regulated by a number of neuropeptides. In the hornworm, Manduca sexta, two neuropeptides interact, namely ecdysis-triggering hormone (ETH) and eclosion hormone. We looked at the effects of ETH in vivo and in vitro, on the brain and the ventral nerve cord to determine the roles played by these hormones. We monitored ecdysis onset and the presence of cGMP and eclosion hormone immunoreactivity. In vivo, only a fraction of larvae lacking the cell bodies containing eclosion hormone, and injected with ETH, were able to undergo ecdysis, with a delayed response. These animals showed strongest cGMP immunoreactivity in the subesophageal and thoracic ganglia, with concomitant reductions in eclosion hormone immunoreactivity in descending axons in comparison with animals not undergoing ecdysis. Animals lacking the brain showed reduced to no cGMP levels in all ganglia. In vitro, isolated CNS preparations lacking the brain initiated ecdysis motor programs after incubation in ETH, with faster onset times than controls, and with reduced cGMP immunoreactivity. If ETH was applied only to the brain of the isolated CNS, cGMP immunoreactivity was noted primarily in the subesophageal and thoracic ganglia, with a decrease in eclosion hormone immunoreactivity in descending axons. ETH addition to the rest of the nerve cord showed reduced eclosion hormone immunoreactivity but little to no cGMP immunoreactivity in any ganglion. Controls showed strong cGMP immunoreactivity in all ganglia, and even greater reductions in eclosion hormone staining after ETH application. These results support previous suggestions that eclosion hormone is required for a positive feedback loop with ETH as well as onset of an inhibitory component, but also suggest that ETH stimulates eclosion hormone release at multiple spike initiation zones. The resultant up regulation of cGMP does not appear to be required for onset of ecdysis. A new model for ecdysis regulation is considered.
蜕皮，或旧表皮的脱落，取决于协调的刻板行为，由许多神经肽调节。在烟青虫，Manduca sexta 中，两种神经肽相互作用，即蜕皮触发激素（ETH）和化蛹激素。我们观察了 ETH 在体内和体外对大脑和腹神经索的影响，以确定这些激素所起的作用。我们监测了蜕皮的开始以及 cGMP 和化蛹激素免疫反应的存在。在体内，只有一部分缺乏含有化蛹激素的细胞体的幼虫，并且注射了 ETH，能够经历蜕皮，反应延迟。这些动物在食道下神经节和胸神经节中显示出最强的 cGMP 免疫反应，同时与未进行蜕皮的动物相比，化蛹激素免疫反应在下行轴突中减少。缺乏大脑的动物在所有神经节中显示出减少或没有 cGMP 水平。在体外，缺乏大脑的分离 CNS 制剂在孵育于 ETH 后启动蜕皮运动程序，其起始时间比对照更快，并且 cGMP 免疫反应减少。如果仅将 ETH 应用于分离 CNS 的大脑，cGMP 免疫反应主要在食道下神经节和胸神经节中观察到，下行轴突中的化蛹激素免疫反应减少。ETH 添加到神经索的其余部分显示化蛹激素免疫反应减少，但在任何神经节中 cGMP 免疫反应都很少或没有。对照显示所有神经节中都有强烈的 cGMP 免疫反应，并且在 ETH 应用后甚至更大程度地减少了化蛹激素染色。这些结果支持先前的建议，即化蛹激素对于与 ETH 以及抑制成分的起始的正反馈环是必需的，但也表明 ETH 刺激化蛹激素在多个脉冲起始区释放。cGMP 的上调似乎不是蜕皮开始所必需的。考虑了一种新的蜕皮调节模型。
