Iincreased GABAA Receptor Zinc Sensitivity Is Associated with Decreased Levels of 1-Subunit Protein Expression and Zinc Staining in Immature Dentate Gyrus.
Abstract number :
1.033
Submission category :
Year :
2000
Submission ID :
3150
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Amy R Brooks-Kayal, Mary Ellen Kelly, Hong Jin, Xiaoling Luo, Douglas A Coulter, Univ of Pennsylvania and Children's Hosp of Phila, Philadelphia, PA; Children's Hosp of Philadelphia, Philadelphia, PA.
Rationale: Our laboratories have previously demonstrated 3-fold lower expression of GABAA Receptor (GABAR) 1 subunit mRNA and 2-fold higher sensitivity of GABARs to zinc inhibition in immature dentate granule cells (DGCs) compared to adult DGCs. We now examine whether these changes are associated with altered 1 protein levels and zinc content in immature dentate gyrus (DG). Methods: Western blots were performed on DG microdissected from rats of 3 different developmental ages (postnatal day (PND) 5-7, 17-21 and adult) using subunit-specific anti- 1 antiserum. 25 g total protein was analyzed for each animal, and 3 animals were evaluated at each developmental timepoint. Parallel blots were performed using anti- -actin antibodies to assure equivalent tissue loading. Timm's staining was performed to assess content and distribution of zinc-containing mossy fibers in 3 animals from each age group. Results: 1 immunolabeling changed significantly during postnatal development (ANOVA p T0.0001), increasing d3-fold between PND 5-7 and PND 17-21 (post-hoc t-test, p T0.0004) and an additional 2-fold between PND 17-21 and adulthood (p T0.0006). Timm's staining demonstrated scant amounts of zinc in the DG hilus in PND 5-7 pups, with a marked increase in the density and extent of zinc-staining by PND 17-21, and a modest additional increase into adulthood. Discussion: Developmental increases in GABAR 1 subunit mRNA in DGCs are accompanied by increases in 1 subunit immunolabeling of greater magnitude, suggesting that both transcriptional and translational control of subunit expression my be occurring during postnatal development. In early postnatal development, low levels of DGC 1 subunit mRNA and protein are expressed and GABARs are highly zinc sensitivity. During this developmental time period, however, relatively low levels of zinc are present in Dentate Gyrus, which may explain why this high GABAR zinc sensitivity is not typically epileptogenic in immature hippocampus. Supported by grants from NIH (NS38595 to ABK and NS32403 to DAC) and Epilepsy Foundation (ABK).