Abstract
麩胺酸是一種重要的興奮性神經傳導物質，普遍地存在於脊椎與無脊椎動物的神經系統中。以反應傳導路徑的類型而言，麩胺酸的受器可分為ionotropic 及 metatropic 兩種。以反應的配體種類來定義，又可區分為數種亞型；前者可再區分為 NMDA 與 Kainate/AMPA ，後者則有 ACPD等數種。在昆蟲體內，除了中樞神經系統之外，在蝗蟲的 neuromuscularjunction，麩胺酸也是一種重要的興奮性與抑制性的神經傳導物質。另外在大白鼠腦下垂體前葉的細胞上，亦被發現具有 NMDA, kainate/AMPA 等類型的麩胺酸受器。在昆蟲的體內，咽側腺體扮演著與脊椎動物體內腦下垂體相對應的角色，分泌及釋放青春激素，調控著蟲體的生長、蛻皮及生殖等作用。在青春激素的分泌過程之中，細胞內鈣離子的存在是必要的條件，將細胞內鈣離子濃度增高可促使咽側腺細胞分泌青春激素。在我們的實驗中發現，麩胺酸的刺激可使得咽側腺細胞內的鈣離子濃度上升，而細胞上的受器很可能是屬於 NMDA 的類型。因此我們認為，麩胺酸的刺激很可能在中樞神經調控咽側腺細胞的細胞內鈣離子濃度與分泌青春激素的功能上佔有很重要的地位。L-glutamate is a neural transmitter for many excitatoryresponses in vertebrate and invertebrate nervous system. It isalso an important transmitter of neuromuscular junctions ininsects. Several subtypes of glutamate receptors (for instanceNMDA and kainate/AMPA) were found in rat anterior pituitarycells. Here I investigate the corpus allatum (CA) cells in aninsect, the analog of the anterior pituitary of vertebrates. Theaim of my study was to certify whenever the glutamate receptoris present in CA cells of the viviparous cockroach D. punctata.Both kind of the ionotropic glutamate receptors are permeable toCa2+, and the G-protein coupled glutamate receptors may increase[Ca2+]i from the intracellular Ca2+ storage pool. So I use the[Ca2+]i as an index to identify the possible presence ofglutamate receptors. The responses of the corpus allatum cellsof Diploptera punctata suggested that at least one subtype ofglutamate receptor, the N-methyl-D-aspartate (NMDA) receptor, ispresent in the cells. Treatment with glutamate causedintracellular calcium concentration raising, that is requiredfor juvenile hormone synthesis. We hypothesize that theglutamate signal may play an important role in regulation ofintracellular calcium concentration and thus juvenile hormonesynthesis.