Abstract
Abstract: :
Purpose: To investigate the effect of eliminating the α2A, α2B, or the α2C–adrenergic receptor subtypes on mouse intraocular pressure (IOP) and its circadian variation. Methods: A microneedle method was used to measure IOP in knockout mice lacking the α2A, α2B, or the α2C–receptor (A–, B–, C–), in α2B wild type mice (B+) and in the background strain mice, C57/Black6 (B6). All mice were maintained in a 12–hour light–dark cycle commencing at 06:00. IOP was measured at 09:00 and 21:00 in 5 groups: B6 (N=9), A– (N=10), B– (N=8), B+ (N=11), and C– (N=10). Results: IOP at 09:00 in B6, A–, B–, B+, and C– mice was 17.1±1.8, 17.7±1.4, 17.1±2.1, 17.6±1.3, and 17.3±0.9 mmHg, respectively (mean ± SD). IOP at 21:00 in the same eyes measured one to two weeks later was 19.6±1.9, 19.2±2.2, 20.5±1.5, 19.7±0.8, and 21.3±2.7 mmHg, respectively. There was no significant difference among the IOP measurements at either time point among these genotypes. Within each genotype, IOP at 21:00 was significantly higher than IOP at 09:00 (B6, B–, B+, and C–: P<0.01 and A–: P<0.05 by the paired t–test). Conclusions: These results indicate that IOP magnitude and circadian variation are not altered by the absence of the α2A, α2B, or α2C–receptor subtypes. We thank Allergan for providing the A–, B–, C–, and B+ mouse subjects. Supported in part by the National Eye Institute EY05990 (RNW) and the Margaret and Robert Boemer Glaucoma Research Fund of the Foundation for Eye Research (MA).
Keywords: intraocular pressure • neurotransmitters/neurotransmitter systems • circadian rhythms