Manipulation of intracellular calcium has no effect on rate of migration of rat autonomic motor neurons in organotypic slice cultures

Migration of neurons is a key step in the formation of the central nervous system, and an increase in internal Ca2+ concentration has been shown to increase the rate of migration of granule cells along radial glial processes in slices of postnatal cerebellum. In embryonic spinal cord, the non-radial migration of autonomic motor neurons from the ventral horn dorsally into the region of the intermediolateral nucleus differs from that of granule cells, so it is possible that the role of Ca2+ may also differ in the migration of these two types of neurons. To investigate this possibility, we made organotypic slice cultures of thoracic spinal cord from rat embryos. In control slices after about one day in vitro, diaphorase-positive autonomic motor neurons had migrated 100 mu m at a rate of 3.6 mu m/h. In experimental slice cultures, we added pharmacological reagents that are known to either increase or decrease internal Ca2+ levels, including some reagents used successfully in the aforementioned granule cell studies. None of the nine reagents had a significant effect on migration speed of autonomic motor neurons in slice cultures. Our results suggest that autonomic motor neuron migration is not regulated by internal Ca2+ levels, and hence this mechanism may not he used universally by all types of neurons. (C) 2000 Elsevier Science Ltd. Published by Elsevier Science Ltd. All rights reserved.