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Glutamatergic Induction of CREB Phosphorylation and Fos Expression in Primary Cultures of the Suprachiasmatic Hypothalamus In Vitro is Mediated by Co‐Ordinate Activity of NMDA and Non‐NMDA Receptors
Author(s) -
Schurov,
McNulty*,
Best,
Sloper,
Hastings
Publication year - 1999
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.1365-2826.1999.00289.x
Subject(s) - kainate receptor , ampa receptor , nmda receptor , creb , glutamatergic , medicine , endocrinology , glutamate receptor , nbqx , chemistry , kainic acid , biology , receptor , biochemistry , transcription factor , gene
Exposure of Syrian hamsters to light 1 h after lights‐off rapidly (10 min) induced nuclear immunoreactivity (–ir) to the phospho‐Ser 133 form of the Ca 2+ /cAMP response element (CRE) binding protein (pCREB) in the retinorecipient zone of the suprachiasmatic nuclei (SCN). Light also induced nuclear Fos‐ir in the same region of the SCN after 1 h. The glutamatergic N‐methyl‐ d ‐aspartate (NMDA) receptor blocker MK801 attenuated the photic induction of both factors. To investigate glutamatergic regulation of pCREB and Fos further, tissue blocks and primary cultures of neonatal hamster SCN were examined by Western blotting and immunocytochemistry in vitro . On Western blots of SCN tissue, the pCREB‐ir signal at 45 kDa was enhanced by glutamate or a mixture of glutamatergic agonists (NMDA, amino‐methyl proprionic acid (AMPA), and Kainate (KA)), whereas total CREB did not change. Glutamate or the mixture of agonists also induced a 56 kDa band identified as Fos protein in SCN tissue. In dissociated cultures of SCN, glutamate caused a rapid (15 min) induction of nuclear pCREB‐ir and Fos‐ir (after 60 min) exclusively in neurones, both GABA‐ir and others. Treatment with NMDA alone had no effect on pCREB‐ir. AMPA alone caused a slight increase in pCREB‐ir. However, kainate alone or in combination with NMDA and AMPA induced nuclear pCREB‐ir equal to that induced by glutamate. The effects of glutamate on pCREB‐ir and Fos‐ir were blocked by antagonists of both NMDA (MK801) and AMPA/KA (NBQX) receptors. In the absence of extracellular Mg 2+ , MK801 blocked glutamatergic induction of Fos‐ir. However, the AMPA/KA receptor antagonist was no longer effective at blocking glutamatergic induction of either Fos‐ir or pCREB‐ir, consistent with the model that glutamate regulates gene expression in the SCN by a co‐ordinate action through both NMDA and AMPA/KA receptors. Glutamatergic induction of nuclear pCREB‐ir in GABA‐ir neurones was blocked by KN‐62 an inhibitor of Ca 2+ /Calmodulin (CaM)‐dependent kinases, implicating Ca 2+ ‐dependent signalling pathways in the glutamatergic regulation of gene expression in the SCN.