Mesce Karen A, Alania Magda, Gaudry Quentin, Puhl Joshua G
Departments of Entomology and Neuroscience, University of Minnesota, St Paul, MN 55108, USA
Department of Biology, Faculty of Exact and Natural Sciences, Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia.
J Exp Biol. 2018 Mar 29;221(Pt 7):jeb175687. doi: 10.1242/jeb.175687.
Blood feeding is an essential and signature activity of the medicinal leech species . Despite keen interest in understanding the neuronal substrates of this behavior, a major component of the nervous system associated with feeding has remained overlooked. In this study, for the first time, we report on the presence and characteristics of five stomatogastric ganglia (STGs) comprising the visceral stomatogastric nervous system (STN) of the leech. Although a brief report was published by Ruth Hanke in 1948 indicating that a ring of three ganglia (not five) was associated with the cephalic ganglia, this information was never integrated into subsequent neurobiological studies of feeding. Here, the anatomical features of the STGs are described, as are the morphological and electrophysiological characteristics of neurons originating in them. We also determined that two of the five STGs (STG-1 and STG-3) each contained two relatively large (ca. 40 µm diameter) serotonergic neurons. The STN was also enriched with dopaminergic and serotonergic arborizations; however, no intrinsic dopaminergic somata were observed. The trajectory of the serotonergic large lateral (LL) neuron, a command-like cell for feeding, was documented to project directly to the STN and not to the jaw and pharyngeal musculature as previously reported, thus reopening the important question of how the LL cell activates and coordinates biting activity with pharyngeal swallowing. Additional studies revealed that the LL cell is excited by blood serum applied to the lip and is strongly inhibited by dopamine. These findings provide a new foundation for understanding the regulation and modulation of neural networks involved in feeding.
吸血是药用蛭类的一项基本且标志性的活动。尽管人们对了解这种行为的神经基质有着浓厚兴趣，但与进食相关的神经系统的一个主要组成部分一直被忽视。在本研究中，我们首次报告了构成水蛭内脏口胃神经系统（STN）的五个口胃神经节（STG）的存在及其特征。尽管露丝·汉克在1948年发表了一篇简短报告，指出有一圈三个神经节（而非五个）与脑神经节相关，但该信息从未被纳入后续关于进食的神经生物学研究中。在此，我们描述了STG的解剖特征，以及源自这些神经节的神经元的形态和电生理特征。我们还确定，五个STG中的两个（STG - 1和STG - 3）各自包含两个相对较大（直径约40 µm）的5 - 羟色胺能神经元。STN中也富含多巴胺能和5 - 羟色胺能分支；然而，未观察到内在的多巴胺能胞体。进食指令样细胞——5 - 羟色胺能大外侧（LL）神经元的投射轨迹被记录下来，发现它直接投射到STN，而不像先前报道的那样投射到颌部和咽部肌肉组织，从而重新开启了LL细胞如何激活并协调咬食活动与咽部吞咽这一重要问题。进一步的研究表明，血清作用于唇部会使LL细胞兴奋，而多巴胺则对其有强烈抑制作用。这些发现为理解参与进食的神经网络的调节和调制提供了新的基础。
