Impaired cholinergic function in cell lines derived from the cerebral cortex of normal and trisomy 16 mice

Murine trisomy 16 is an animal model of human Down's syndrome. We have succ essfully established permanently growing cell lines from the cerebral corte x of normal and trisomy 16 foetal mice using an original procedure. These l ines, named CNh (derived from a normal animal) and CTb (derived from a tris omic foetus), express neuronal markers. Considering that Down's syndrome ex hibits cholinergic deficits, we examined cholinergic function in these line s, using incorporation of [H-3]-choline and fractional release studies. Aft er 1, 3 and 5 min of [H-3]-choline incubation, CTb cell uptake was lower by similar to 50% compared to controls. Hemichollinium-3 significantly reduce d the incorporation of [H-3]-choline in both CNh and CTb cells at high conc entration (10 mu M), suggesting high-affinity choline transport. However, C Tb cells exhibited greater sensitivity to the blocker. For fractional relea se experiments, the cells were stimulated by K+ depolarization, glutamate o r nicotine. When depolarized, CTb cells showed a 68% reduction in fractiona l release of [H-3]-acetylcholine compared to CNh cell line, and a 45% reduc tion when stimulated by nicotine. Interestingly, glutamate induced similar levels of release in both cell types. The results indicate the existence of cholinergic dysfunction in CTb cells when compared to CNh, similar to that reported for primary cultures of trisomy 16 brain tissue (Fiedler et al., 1994, Brain Res., 658, 27-32). Thus, the CTb cell line may serve as a model for the study of Down's syndrome pathophysiology.