Calcitonin gene-related peptide identifies spinal motoneurons in vitro

Cell dissociation of E6 chick spinal cord followed by isolation of larger low-density cells by using a discontinuous density metrizamide gradient resulted in the obtention of a motoneuron-enriched fraction of cells. These cells were cultured in the presence of horse serum and muscle extract for a period of 8 days and examined for the presence of calcitonin gene-related peptide. More than 90% of such cells were positive for calcitonin gene-related peptide. When E14 spinal cord was examined, calcitonin gene-related peptide was present only in the axons of primary sensory neurons and in the somas of motoneurons in the ventral horns. It is concluded that more than 90% of the neurons in our cultures are motoneurons.