ABSTRACT
Purpose: To investigate the relationship between intraocular pressure (IOP) and GABA receptors within the arcuate nucleus (ARC). Methods: In the chronic high IOP rat model, ibotenic acid (IBO) was injected to induce impairment of the ARC, and IOP was measured at the 0, 1, 2, 3, and 4 week time points with a Tono-Pen. To assess the expression of GABA-A/B receptors within the ARC under persistent high IOP, we performed immunofluorescence (IF) and immunohistochemical (IHC) staining at 2 weeks and 4 weeks. Furthermore, we treated the ARC with GABA-A/B receptor antagonists separately, and IOP was evaluated, as well as retinal ganglion cell apoptosis in the chronic high IOP rat model. In the following induced high IOP animal model, the expression of GABA-A/B receptors within the ARC was evaluated in DBA/2J mice which developed progressive eye abnormalities spontaneously that closely mimic human hereditary glaucoma. Results: Compared with the control group, statistically significant downregulation of IOP was noted due to the IBO injection into the ARC at the 2, 3, and 4 week time points (p<0.05). Persistent high IOP elicited increased expression of the GABA-A/B receptors in the ARC compared with the control group (p<0.01). In addition, treatment with GABA-A/B receptor antagonists separately caused a decrease in the IOP, along with reduced retinal ganglion cell apoptosis (p<0.01). In the DBA/2J mice, the expression of the GABA receptors was statistically significantly increased (p<0.01). Conclusions: GABA-A/B receptors in the ARC may be involved in regulation of IOP, and pathologically high IOP affects the expression of GABA-A/B receptors in the ARC.
Subject(s)
Arcuate Nucleus of Hypothalamus/metabolism , Disease Models, Animal , Intraocular Pressure/physiology , Ocular Hypertension/metabolism , Receptors, GABA-A/metabolism , Receptors, GABA-B/metabolism , Animals , Apoptosis , Arcuate Nucleus of Hypothalamus/drug effects , Excitatory Amino Acid Agonists/pharmacology , Fluorescent Antibody Technique, Indirect , GABA-A Receptor Antagonists/pharmacology , GABA-B Receptor Antagonists/pharmacology , Ibotenic Acid/pharmacology , Immunoenzyme Techniques , In Situ Nick-End Labeling , Male , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Rats , Rats, Sprague-Dawley , Retinal Ganglion Cells/pathology , Tonometry, Ocular , Transcription Factor Brn-3A/metabolismABSTRACT
FLOWERING LOCUS C (FLC), encoding a MADS-domain transcription factor in Arabidopsis, is a repressor of flowering involved in the vernalization pathway. This provides a good reference for Brassica species. Genomes of Brassica species contain several FLC homologues and several of these colocalize with flowering-time QTL. Here the analysis of sequence variation of BrFLC1 in Brassica rapa and its association with the flowering-time phenotype is reported. The analysis revealed that a G-->A polymorphism at the 5' splice site in intron 6 of BrFLC1 is associated with flowering phenotype. Three BrFLC1 alleles with alternative splicing patterns, including two with different parts of intron 6 retained and one with the entire exon 6 excluded from the transcript, were identified in addition to alleles with normal splicing. It was inferred that aberrant splicing of the pre-mRNA leads to loss-of-function of BrFLC1. A CAPS marker was developed for this locus to distinguish Pi6+1(G) and Pi6+1(A). The polymorphism detected with this marker was significantly associated with flowering time in a collection of 121 B. rapa accessions and in a segregating Chinese cabbage doubled-haploid population. These findings suggest that a naturally occurring splicing mutation in the BrFLC1 gene contributes greatly to flowering-time variation in B. rapa.