Acta Neuropathol (Berl) (1983)59:17t - 182 Acta Neuropa~ologica 9 Springer-Verlag 1983 Effects of GABA, Glycine, and Sodium Barbiturate on Dendritic Growth in vitro S. J. Baloyannis 1, K. Karakatsanis 2, J. Karathanasis 1, M. Apostolakis 1, and A. Diacoyannis 1 1 Dept. of Neurology and 2 Dept. of Medical Physics, School of Medicine, Aristotelian University, Thessaloniki, Greece Summary. Dendritic growth and dendritic arboriza- tion of both the large neurons of the cerebral and the cerebellar cortex and the small bipolar neurons were studied in vitro under normal feeding conditions and under the influence of GABA, glycine, and sodium barbiturate. By the end of week 1 the neurons cultured in nor- mal nutrient developed primary dendritic shafts, dem- onstrating a tendency for bifurcation. By the end of week 2 the neurons appeared as numerous secondary dendritic branches studded with spines. The dendritic development and growth proceeded continuously un- til week 12 when no further growth and differentia- tion of the dendritic arborization was noted. Feeding medium enriched with GABA or glycine enhanced dendritic growth and dendritic arborization in vitro. On the contrary, feeding medium contained sodium barbiturate, partially suppressed dendritic growth and dendritic arborization in the neurons of the cerebral and the cerebellar explants. Ultrastructural studies revealed that sodium barbiturate partially sup- pressed the synapse formation between the neuronal circuits of the cortical explants. Key words: Dendritic growth - Tissue culture - GABA - Glycine - Sodium barbiturate - Synapses in vitro Introduction Since Harrison introduced the culture of nervous tissue in vitro in 1907, this technique has been extensively used, with improving modifications, for the study of the growth of nervous tissue under normal and Offprh2t requests to: Stavros J. Baloyannis, Associate Professor (ad- dress see above) noxious conditions. Although initially the main interest was focused on axonal growth, several authors de- scribed the growth of the dendrites and the dendritic arborizations in vitro, using the Golgi method (Morest 1969) or the electron microscope (Sotelo and Palay 1968; Hinds and Hinds 1972; Vaughn et al. 1974; Privat 1975). In the present study we first examined the den- dritic growth in vitro of a large number of cells from the cerebral cortex and the cerebellum, using light and electron microscopy, and then we defined the ef- fects of GABA, glycine, and sodium barbituraterate on the dendritic growth in vitro. Material and Methods Newborn Lewis rats were killed by exsanguination. Their brains were removed and divided sagittally into 20 slices each. Explants (2 • 2 mm) were isolated from the vermis and the hemispheres of the cerebellum as well as from the frontal region of the cerebrum, placed on collagen-coated cover slips, and maintained within rol- ler tubes in a nutrient composed of 20~ fetal calf serum, 30% eagles minimal essential medium plus 8 % glucose. Eight explants isolated from the vermis, the hemispheres of the cerebellum and the frontal region of the cerebrum were placed on collagen-coated cover slips and set in culture within roller tubes in a medium com- posed of 20 % fetal calf serum,. 30 ~ Eagle's minimal essential me- dium, 8 % glucose, and 1~ GABA (Serva Feinbiochemica, Heidel- berg, FRG). Eight explants isolated from the above mentioned regions were placed in collagen-coated cover slips and maintained within roller tubes in a nutrient composed of 20 ~ fetal calf serum, 30 % Eagle's minimal essential medium, 8 ~ glucose plus 1~ glycine (Serva Feinbiochemica, Heidelberg, FRG). Eight more explants, isolated from the same regions as men- tioned above, were placed on collagen-coated cover slips and set in culture within roller tubes in a medium composed of 20 % fetal calf serum, 30 % Eagle's minimal essential medium, 8 % glucose plus 1~ sodium barbiturate (Copper, S. A. Hellas). All of the explants were cultured in vitro at a temperature of 37~ They were examined twice a week with a phase contrast microscope on Maximov plates. Photographs were taken, and their growth was estimated.