Abstract

We have established hippocampal cell lines from normal and trisomy 16 fetal mice, a model of human trisomy 21. Both cell lines, named H1b (derived from a normal animal) and HTk (trisomic) possess neuronal markers by immunohistochemistry (enolase, synaptophysin, microtubule associated protein-2, and choline acetyltransferase) and lack glial markers (glial fibrillary acidic protein and S-100). Also, we evaluated intracellular Ca2+ levels ([Ca2+]i) in response to neurotransmitter agonists, in cells loaded with the fluorescent Ca2+ indicators Indo-1 and Fluo-3. Both cell lines responded to glutamatergic stimuli induced by glutamate, N-methyl-D-aspartate, I-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazole propanoic acid or kainate. Glutamate responses were only partially prevented by addition of 5 mM EGTA and the metabotropic glutamate receptor agonist, trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD), increased [Ca2+]i in both cell types. These results confirm the presence of glutamatergic metabotropic receptors. In glutamate-induced responses, HTk cells exhibited slower time-dependent decay kinetics than H1b cells. Cholinergic agonists (nicotine and muscarine) induced a rapid, transient increase in [Ca2+]i in both cell types. Furthermore, some cells were sensitive to histamine and norepinephrine. All responses to the aforementioned agonists were prevented by addition of specific antagonists. We also studied incorporation and release of [3H]choline in the cells, and observed no differences in uptake parameters. However, release induced by K+ and nicotine depolarization was greatly reduced in HTk cells. The results show that H1b and HTk cells retain neuronal characteristics and respond to specific neurotransmitter stimuli. The HTk differences could be related to neuronal pathophysiology in Down syndrome. © 2002 Elsevier Science (USA).