GABAB receptor expression and cellular localization in gerbil hippocampus after transient global ischemia

Using in situ hybridization, the expression of the GABA receptor subtype B subunit 1 (GABAB R1) and subunit 2 (GABAB R2) following transient global ischemia in the gerbil hippocampus was investigated. In sham-operated animals, mRNAs of both subunits were mainly detected in hippocampal pyramidal cells and interneurons with lower expression levels of the GABAB R2 in the CA1 field. Four days after transient cerebral ischemia, neuronal message decreased in conjunction with neuronal death and both receptor subunits disappeared from the pyramidal cell layer. However, GABAB R1 and GABAB R2 were still expressed in a few cells. In situ hybridization of the GABA synthesizing enzyme glutamic acid decarboxylase 67 (GAD67) remained unchanged after the ischemic insult. Double-labeling experiments revealed that in the postischemic hippocampus GABAB R1 and GABAB R2 were not present in GFAP-reactive astrocytes, but that the surviving parvalbumin-containing interneurons possessed GABAB R1 and GABAB R2 mRNA.