Expression of ionotropic glutamate receptor subunit mRNAs by paraventricular corticotropin-releasing factor (CRF) neurons

To determine whether paraventricular corticotropin-releasing factor (CRF) neurons express NMDA, AMPA or kainate-preferring glutamate receptors, we have colocalized, by in situ hybridization (ISH), transcripts of various glutamate receptor subunit genes with the CRF messenger RNA on doublet adjacent sections of the rat hypothalamus. We found that more than 70% of CRF-positive neurons contain the NMDA receptor subunit NR1 mRNA whereas NR2A and NR2B subunit mRNAs were not detectable in CRF cells. A significant proportion of identified CRF cells express AMPA receptor subunit GluRA (46%), GluRB (21%) as well as the kainate-preferring receptor subunit KA2 (31%) mRNAs. These results support the hypothesis that the excitatory transmitter glutamate may directly influence CRF neurons through NMDA as well as non-NMDA receptors.