Abstract
Abstract: :
Purpose: To characterize the time course of mouse intraocular pressure (IOP) under two anesthetic protocols, ketamine alone or ketamine + xylazine. Method:Two groups of Black Swiss mice received intraperitoneal anesthesia: either ketamine alone (250mg/kg) or a mixture of ketamine (100mg/kg) + xylazine (9 mg/kg). Starting as soon as the mouse displayed no pedal reflex, the time course of IOP was measured continuously with the Servo–Null Micropipette system (SNMS) at a frequency of 3 Hz, using a micropipette with an inner tip diameter of 7.5–10 µm. Results: In the ketamine only group, the IOP remained essentially stable from 10 min to 24 min after anesthesia injection. The slope of the IOP vs. time relationship was –0.05±0.02 mmHg/min. The mean IOP drop at 24 min was 0.3±1.2 mmHg (P >0.8) from reading at 10 min. In the ketamine + xylazine group, there was a continuous fall of IOP from 8min to 20 min. The rate of decrease of IOP was –0.53±0.04 mmHg/min. The mean IOP drop at 20 min was 7.1±0.9 mmHg compared to 8min, and this change corresponded to a 34% drop from the initial reading (P <0.0001). Conclusion: Mouse IOP was relatively stable under ketamine anesthesia, but ketamine + xylazine induced a significant IOP lowering during the 8–20 min after anesthetic injection. [CR:N. Support: NIH research grant EY 13624, core grant EY 01583 and RPB]
Keywords: intraocular pressure • electrophysiology: non–clinical • drug toxicity/drug effects