Improved organotypic cell culture model for analysis of the neuronal circuit involved in the monosynaptic stretch reflex.

Knowledge regarding neuronal circuit formation is central for the understanding of the vast network making up the brain. It is therefore necessary to find novel ways to analyze the mechanisms involved in well-defined neural circuits. We present an improved in vitro model of the monosynaptic stretch reflex circuit, based on primary organotypic cell cultures. By using limb tissue as a source of muscle fibers instead of circumspinal tissue we could make the in vitro system more in vivo like in the sense that it focuses on the stretch reflex involving limb muscles. Furthermore, our analyses showed that this procedure allows muscle fibers to follow the normal developmental pattern. Particularly interesting was the finding of slow tonic myosin heavy chain expressing muscle fibers, a developmental marker for muscle spindles, in the cultures showing that this system has the potential to contain the complete reflex circuits.