An in vitro rabbit retina model to study electrophysiologic and metabolic function during and following ischemia

Most in vitro studies involving neuronal ischemia use biochemical measures and/or cell counting to assess cellular death. We describe an in vitro rabbit retina model in which we measured glucose utilization, lactate production, and light-evoked compound action potentials (CAPs) to assess metabolic and functional recovery following ischemia. Under control conditions, retinal glucose utilization and lactate production (n = 7), as well as CAPs (n = 8) remained quite constant for 6-8 h. During ischemia (glucose reduced from 6 to 1 mM and oxygen from 95 to 15%), glucose utilization and lactate production fell to 50%. CAPs fell to 50% in 3-4 min, and to 0% in 8-10 min. Recovery during 3-4 h of 'return-to-control' was dependent upon the length of ischemia. Glucose utilization recovered to 63% after 1 h (n = 4) and to 18% after 2 h of ischemia (n = 6, P < 0.001). Lactate production recovered to 77% after 1 h (n = 4) and to 54% after 2 h of ischemia (n = 6, P < 0.001). CAPs returned to 51, 15, and 0.13% of the control responses after 0.5 h (n = 7), 1 h (n = 8), and 2 h (n = 5) of ischemia, respectively (P < 0.001). This avascular, blood-brain barrier-free preparation provides an opportunity to use both metabolic and functional criteria to test protection against neuronal ischemia.