Comparative responsiveness of early chick embryo brainstem and spinal cord neurons to target-conditioned medium.

Neurons from the early trigeminal (V) region of the basal plate and from the early ventral spinal cord of chick embryos were dissociated. Their responsiveness to muscle-conditioned medium (MCM) derived from age-matched appropriate and inappropriate target was compared. The V neurons responded to appropriate but not inappropriate MCM by enhanced survival and increased neurite production. Conversely, there were no differences in these measures in spinal cord neurons cultured in control medium and in MCM derived either from appropriate or inappropriate (trigeminal) target. The differences in specificity expressed by these two early populations is discussed.