Bioelectric activity is required for regional specificity of sensory ganglion projections to spinal cord explants cultured in vitro.

Chronic blockade of spontaneous nerve impulses by means of tetrodotoxin leads to abnormally diffuse afferent projections into spinal cord cross-sections cultured for two to six weeks in vitro. In addition, even untreated explants which show a low level of spontaneous cord discharges failed to develop the normal degree of dorsal pathway selectivity. It is therefore concluded that centrally generated neuronal activity may play an important role in eliminating 'exuberant' connections which, during early development, are transiently present in this part of the nervous system.