Effects of Brimonidine on Microglia Morphology in the Transient Retinal Ischemia Model

Abstract

Background:This study aimed to investigate the effects of brimonidine on microglia cell morphology by creatinga transient retinal ischemia model in rats. Methods:In the right eyes of male Wistar rats (n= 12), a transient retinal ischemia model was created. The ratswere divided into three groups: (1) eyes treated with topical brimonidine in the transient retinal ischemia model,(2) sham-treated eyes, and (3) control eyes. Four main phenotypes (ramified, primed, reactive, and amoeboid-phagocytic) of Iba-1 positive microglia cells were examined in the retinal layers. Results:In the transient retinal ischemia model, the number of Iba-1 positive microglia cells was 100.67±7.50 cellsin the sham group and 57.67±14.64 cells in the topical brimonidine group. The decrease in the total number of Iba-1 positive microglial cells was statistically significant (p<0.05). When we compared ramified and primed microgliacells, there was no statistically significant difference between the groups. The number of amoeboid-phagocyticmicroglial cells was 9.5±1.29 cells in the sham treatment group and 2.25±0.50 cells in the topical brimonidinegroup (p<0.05). There was a statistically significant decrease in the number of reactive and amoeboid cells. Conclusion:Studies in the central nervous system in rats demonstrated that cell metabolism and functions werechanged after acute injury and that microglia transformed from a ramified form to an amoeboid-phagocytic form.In this study, the decrease in the transition of cells from ramified to reactive and amoeboid forms showed us thattopical brimonidine treatment could have neuroinflammation suppressor features.