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Ionotropic and Metabotropic Glutamate Receptor Agonist‐Induced [Ca 2+ ] i Increase in Isolated Rat Supraoptic Neurons
Author(s) -
Hattori Yukio,
Shibuya Izumi,
Tanaka Keiko,
Kabashima Narutoshi,
Ueta Yoichi,
Yamashita Hiroshi
Publication year - 1998
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1998.00219.x
Subject(s) - metabotropic glutamate receptor , metabotropic glutamate receptor 1 , metabotropic receptor , metabotropic glutamate receptor 5 , kainate receptor , metabotropic glutamate receptor 2 , metabotropic glutamate receptor 6 , glutamate receptor , metabotropic glutamate receptor 7 , ampa receptor , chemistry , agonist , nmda receptor , acpd , medicine , endocrinology , long term depression , biology , receptor , biochemistry
In the present study, the effects of glutamate and of agonists for ionotropic and metabotropic glutamate receptors on intracellular Ca 2+ concentration ([Ca 2+ ] i ) were investigated in neurons of the rat supraoptic nucleus (SON). We used the intracellular Ca 2+ imaging technique with fura‐2, in single magnocellular neurons dissociated from the SON of rats. Glutamate (10 −6 −10 −4 M) evoked a dose‐dependent increase in [Ca 2+ ] i . The glutamate agonists exerted similar effects, although with some differences in the characteristics of their responses. The [Ca 2+ ] i response to NMDA was smaller than those of glutamate or the non‐NMDA receptor agonists, AMPA and kainate, but was significantly enhanced by the removal of extracellular Mg 2+ . Glutamate, as well as quisqualate, an agonist for both ionotropic and metabotropic glutamate receptors, evoked a [Ca 2+ ] i increase in a Ca 2+ ‐free condition, suggesting Ca 2+ release from intracellular Ca 2+ stores. This was further evidenced by [Ca 2+ ] i increases in response to a more selective metabotropic glutamate receptor agonist, t‐ACPD, in the absence of extracellular Ca 2+ . Furthermore, the quisqualate‐induced Ca 2+ release was abolished by the selective metabotropic glutamate receptor antagonist, (S)‐4‐carboxyphenylglycine. The results suggest that metabotropic glutamate receptors as well as non‐NMDA and NMDA receptors are present in the SON neurons, and that activation of the first leads to Ca 2+ release from intracellular Ca 2+ stores and the activation of the latter two types induces Ca 2+ entry. These dual mechanisms of Ca 2+ signalling may play a role in the regulation of SON neurosecretory cells by glutamate.