The Effect Of Galanin On Choroidal Blood Flow In Rabbits And Rats

Abstract

Purpose: : To study the effect of galanin on choroidal blood flow (ChorBF) in anesthetized rabbits and rats with Laser Doppler flowmetry.

Methods: : In anesthetized New Zealand white rabbits (n=8) mean arterial pressure (MAP) and intraocular pressure (IOP) were measured by direct cannulation of the central ear artery and the vitreous, respectively. Laser Doppler flowmetry (LDF) was used to measure ChorBF. Galanin was administrated intravenously with a concentration of 1mg/kg/h.In Brown Norway rats mean arterial pressure (MAP) was measured by cannulation of the femoral artery. ChorBF measurements (n=6) were performed with non contact LDF. Galanin was infused at a dose of 1mg/kg/h and 3mg/kg/h.Control experiments in rat and rabbit forehead skin were performed to reproduce the known galanin effect on skin blood flow. Since the rabbit specific galanin sequence has not been identified up to now, rat specific galanin was used in both species.

Results: : In both species no significant effect on ChorBF was detectable. However in 3/8 experiments choroidal vasodilation was measured in rabbit but not in rat. Nevertheless, control experiments in rat forehead skin revealed an increase in blood flow (36%) after 1mg/kg/h galanin application. The increase of galanin concentration to 3mg/kg/h still had no effect on choroidal blood flow. Control experiments in rabbit forehead skin showed no effect.

Conclusions: : In the present study the administration of galanin revealed no significant effect on choroidal blood flow in the species investigated. The discrepancy in choroidal blood flow in the rabbit group needs to be further explored. Differences in the amino acid sequence or receptor binding properties between the used rat specific galanin and rabbit galanin might be responsible for the effect on rat skin blood flow, which was not observed in rabbits.

Keywords: blood supply • choroid