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 language | English |
---|---|
Pages (from-to) | 10852-10863 |
Number of pages | 12 |
Journal | Journal of Neuroscience |
Volume | 28 |
Issue number | 43 |
DOIs | |
Publication status | Published - Oct 22 2008 |
Externally published | Yes |
Keywords
- Calcium
- Depolarization
- Glutamate transporters
- Patch clamp
- Pineal
- Secretion
ASJC Scopus subject areas
- Neuroscience(all)