Developmental changes in cultured neurones from chick embryo cerebral hemispheres. An ultrastructural and neurochemical study.

The acquisition of ultrastructural and neurochemical properties was studied during the development of neurones from 8-day-old chick embryo cerebral hemispheres, cultivated on polylysine-coated surfaces. The first contacts suggestive of synaptic profiles were observed after 3 days of culture. From the 6th day, junctions with significant thickening of the postsynaptic element and many presynaptic vesicles could be seen. Synaptic endings contained predominantly dense-cored vesicles. These cultured neurones acquired dopaminergic properties during their development: (1) 95% of the cells exhibited glyoxylic acid-induced fluorescence; (2) tyrosine hydroxylase and dopa decarboxylase activities were present and increased with time in culture, but dopamine-beta-hydroxylase activity was undetectable. Choline acetyltransferase activity remained at a very low level at all stages of culture. It is suggested that when cultured in the total absence of glial cells, the neurones of embryonic chick cerebral hemispheres give no evidence of cholinergic mechanisms, but display a number of dopaminergic characteristics.