![]() ![]() Anesthesia was titrated to achieve a depth facilitating stable anterior chamber cannulation and perfusion. Joseph, MO), xylazine (6–8.5 mg/kg, AnaSed Lloyd Laboratories, Shenandoah, IA), and acepromazine (1.5–2.5 mg/kg Boehringer Ingelheim, St. Mice were anesthetized with a mixture of ketamine (60–85 mg/kg, Ketaject Phoenix Pharmaceutical, Inc., St. All perfusion measurements were performed between 12 PM and 5 PM. The mice were raised and housed in air-filtered clear cages with a bedding of pine shavings, subjected to a 12 h:12 h light-dark cycle, and fed ad libitum. C57BL/6 mice, aged 3–4 months, were purchased from Charles River Laboratories (Wilmington, MA). Approval was obtained from the University of Southern California Institutional Animal Care and Use Committee (IACUC). Mouse experiments were performed in accordance with the Association for Research in Vision and Ophthalmology Statement for Use of Animals in Ophthalmic and Vision Research. This methodology was applied to live C57BL/6 mice in which pressure stability and reproducibility, outflow facility, and perfusion system resistance were characterized. The feedback control system tracked transduced pressure to automatically vary pump perfusion flow rate to maintain pressure at a predetermined level. We conducted constant-pressure perfusion by one-needle cannulation using a microsyringe pump electronically coupled to a pressure transducer and feedback control system. Given the small cornea and anterior chamber space of mice, it would seem preferable if perfusion studies were conducted by one-needle cannulation instead of two-needle cannulation techniques often used in larger primate eyes and adapted for mice. We have established apparatus and approaches for constant pressure anterior chamber perfusion in live mice. Not surprisingly, recent efforts to measure outflow dynamics have focused on enucleated eyes instead of live mouse eyes. Perfusing the anterior chamber of live mice is thus expected to be technically challenging. The mouse eye is an order of magnitude smaller than the primate eye, with mouse anterior chamber volume about 5 µl compared with 135 µl in rhesus and 250 µl in humans. Anterior chamber microperfusion in live mice to measure aqueous outflow dynamics by different approaches has been reported. ![]() Mouse and primate aqueous outflow systems share similar morphology and physiology, and many engineered mouse strains are available, making the mouse a promising model for studying aqueous outflow dynamics relevant to human biology and glaucoma. This approach is potentially useful for exploring aqueous drainage tissue biology, physiology, and pharmacology in live mice. Perfusion measurements were reproducible. No histological disruption of the drainage tissue was seen following perfusion.Ĭonclusions: Predetermined pressure was stably maintained during constant-pressure perfusion of live mouse eyes by a method using feedback-controlled coupling of pressure and flow along with single-needle anterior chamber cannulation. Perfusion system resistance (0.5 mmHg/min/µl) was negligible relative to the ocular outflow resistance (147 mmHg/min/µl) at physiologically relevant perfusion pressures of 15–35 mmHg. The total outflow facility was 0.0066 µl/min/mmHg. The relationship between flow rate and pressure was linear for perfusions between 15 and 35 mmHg. The average coefficient of variation for repeat pressure and flow rate measurements was 0.0005 and 0.127, respectively. The coefficient of pressure variation over time during perfusion at a preset pressure was <0.001. Constant pressure was quickly attained and stably maintained. Results: Twenty live mice underwent perfusion. We characterized the following in C57BL/6 mice aged 3–4 months in vivo: (i) pressure stability, (ii) pressure and flow rate reproducibility, (iii) total outflow facility, and (iv) anterior segment histology after perfusion. Perfusion was by single-needle cannulation. Methods: We established a microperfusion system that maintains a constant preset pressure in the anterior chamber of live mice by automatically regulating the microsyringe pump flow rate with a computer-controlled voltage feedback loop. Purpose: To describe live mouse, anterior chamber constant-pressure perfusion by an approach using feedback-controlled coupling of pressure and flow to maintain a preset pressure. ![]()
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