Elekes Károly, Hiripi László, Balog Gábor, Maász Gábor, Battonyai Izabella, Khabarova Marina Yu, Horváth Réka, Voronezhskaya Elena E
1 Department of Experimental Zoology, Balaton Limnological Institute, MTA Centre for Ecological Research, Hungarian Academy of Sciences , H-8237 Tihany , Hungary.
2 Institute of Developmental Biology, Russian Academy of Sciences , Moscow 119334 , Russia.
Acta Biol Hung. 2018 Sep;69(3):225-243. doi: 10.1556/018.68.2018.3.1.
Hatching is an important phase of the development of pulmonate gastropods followed by the adult-like extracapsular foraging life. Right before hatching the juveniles start to display a rhythmic radula movement, executed by the buccal complex, consisting of the buccal musculature (mass) and a pair of the buccal ganglia. In order to have a detailed insight into this process, we investigated the serotonergic regulation of the buccal (feeding) rhythm in 100% stage embryos of the pond snail, Lymnaea stagnalis, applying quantitative immunohistochemistry combined with the pharmacological manipulation of the serotonin (5-HT) synthesis, by either stimulating (by the 5-HT precursor 5-hydroxytryptophan, 5-HTP) or inhibiting (by the 5-HT synthesis blocker para-chlorophenylalanine, pCPA) it. Corresponding to the direction of the drug effect, significant changes of the fluorescence intensity could be detected both in the cerebral ganglia and the buccal complex. HPLC-MS assay demonstrated that 5-HTP increased meanwhile pCPA decreased the 5-HT content both of the central ganglia and the buccal complex. As to the feeding activity, 5-HTP induced only a slight (20%) increase, whereas the pCPA resulted in a 20% decrease of the radula protrusion frequency. Inhibition of 5-HT re-uptake by clomipramine reduced the frequency by 75%. The results prove the role of both central and peripheral 5-HTergic processes in the regulation of feeding activity. Application of specific receptor agonists and antagonists revealed that activation of a 5-HT1-like receptor depressed the feeding activity, meanwhile activation of a 5-HT6,7-like receptor enhanced it. Saturation binding plot of [3H]-5-HT to receptor and binding experiments performed on membrane pellets prepared from the buccal mass indicated the presence of a 5-HT6-like receptor positively coupled to cAMP. The results suggest that 5-HT influences the buccal (feeding) rhythmic activity in two ways: an inhibitory action is probably exerted via 5-HT1-like receptors, while an excitatory action is realized through 5-HT-like receptors.
孵化是肺螺亚纲腹足类动物发育的一个重要阶段，之后便是类似成体的囊外觅食生活。就在孵化前，幼体开始表现出有节奏的齿舌运动，由口腔复合体执行，该复合体由口腔肌肉组织（团块）和一对口腔神经节组成。为了深入了解这一过程，我们通过定量免疫组织化学结合血清素（5-羟色胺，5-HT）合成的药理学操作，研究了池塘螺（椎实螺）100%阶段胚胎口腔（摄食）节律的血清素能调节，方法是刺激（使用5-HT前体5-羟色氨酸，5-HTP）或抑制（使用5-HT合成阻滞剂对氯苯丙氨酸，pCPA）血清素合成。与药物作用方向一致，在脑神经节和口腔复合体中均能检测到荧光强度的显著变化。高效液相色谱-质谱分析表明，5-HTP增加了，而pCPA降低了中枢神经节和口腔复合体中的5-HT含量。至于摄食活动，5-HTP仅引起轻微（20%）增加，而pCPA导致齿舌伸出频率降低20%。氯米帕明抑制5-HT再摄取使频率降低75%。结果证明了中枢和外周5-HT能过程在调节摄食活动中的作用。应用特异性受体激动剂和拮抗剂表明，激活5-HT1样受体可抑制摄食活动，同时激活5-HT6,7样受体可增强摄食活动。[3H]-5-HT与受体的饱和结合曲线以及在从口腔团块制备的膜沉淀物上进行的结合实验表明存在一种与cAMP正偶联的5-HT6样受体。结果表明，5-HT以两种方式影响口腔（摄食）节律活动：抑制作用可能通过5-HT1样受体发挥，而兴奋作用则通过5-HT样受体实现。
