Glutamate transporter-mediated glutamate secretion in the mammalian pineal gland

Mean Hwan Kim, Shunsuke Uehara, Akiko Muroyama, Bertil Hille, Yoshinori Moriyama, Duk Su Koh

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14 Citations (Scopus)

Abstract

Glutamate transporters are expressed throughout the CNS where their major role is to clear released glutamate from presynaptic terminals. Here, we report a novel function of the transporter in rat pinealocytes. This electrogenic transporter conducted inward current in response to L-glutamate and L- or D-aspartate and depolarized the membrane in patch-clamp experiments. Ca 2+ imaging demonstrated that the transporter-mediated depolarization induced a significant Ca2+ influx through voltage-gated Ca 2+ channels. The Ca2+ rise finally evoked glutamate exocytosis as detected by carbon-fiber amperometry and by HPLC. In pineal slices with densely packed pinealocytes, glutamate released from the cells effectively activated glutamate transporters in neighboring cells. The Ca2+ signal generated by KCl depolarization or acetylcholine propagated through several cell layers by virtue of the regenerative "glutamate-induced glutamate release." Therefore, we suggest that glutamate transporters mediate synchronized elevation of L-glutamate and thereby efficiently downregulate melatonin secretion via previously identified inhibitory metabotropic glutamate receptors in the pineal gland.

Original languageEnglish
Pages (from-to)10852-10863
Number of pages12
JournalJournal of Neuroscience
Volume28
Issue number43
DOIs
Publication statusPublished - Oct 22 2008

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Keywords

  • Calcium
  • Depolarization
  • Glutamate transporters
  • Patch clamp
  • Pineal
  • Secretion

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Kim, M. H., Uehara, S., Muroyama, A., Hille, B., Moriyama, Y., & Koh, D. S. (2008). Glutamate transporter-mediated glutamate secretion in the mammalian pineal gland. Journal of Neuroscience, 28(43), 10852-10863. https://doi.org/10.1523/JNEUROSCI.0894-08.2008