Long-duration perforated patch recordings from spinal interneurons of adult mice

It has been very difficult to record from interneurons in acute slices of the lumbar spinal cord from mice >3 wk of age. The low success rate and short recording times limit in vitro experimentation on mouse spinal networks to neonatal and early postnatal periods when locomotor networks are still developmentally immature. To overcome this limitation and enable investigation of mature locomotor network neurons, we have established a reliable procedure to record from spinal cord neurons in slices from adult, behaviorally mature mice of any age. Two key changes to the established neonate procedure were implemented. First, we remove the cord by a dorsal laminectomy from a deeply anesthetized animal. This enables respiration and other vital functions to continue up to the moment the maximally oxygenated lumbar spinal cord is removed, improving the health of the slices. Second, since adult spinal cord interneurons appear more sensitive to the intracellular dialysis that occurs during whole cell recordings, we introduced perforated patch recordings to the procedure. Stable recordings up to 12 h in duration were obtained with our new method. This will allow investigation of changes in mature neuronal properties in disease states or after spinal cord injury and allow prolonged recordings of responses to drug application that were previously impossible.