The effect of nerve growth factor on cholinergic cells in primary fetal striatal cultures: characterization by in situ hybridization

In situ hybridization using ³⁵S-labeled antisense oligonucleotide probes for choline acetyltransferase (ChAT), and m1 and m2 muscarinic receptors was employed to monitor the effect of nerve growth factor (NGF) on cholinergic cells in mixed neuronal-glial striatal brain cultures prepared from E16/E17 rat embryos. In cultures treated with NGF, cells reactive to the ChAT oligonucleotide probe were significantly larger than cells in untreated cultures. In addition, there was a significant increase in the number of silver grains over reactive cells in cultures exposed for 9-10 days to exogneous NGF. Similar results were obtained with an oligonucleotide probe specific for m2 muscarinic receptors: in NGF-treated cultures, cells reactive to the m2 receptor probe were significantly larger and had more silver grains than cells from non-treated cultures. On the other hand, no significant effect of NGF on cell size or on the number of grains was observed for cells reactive to an m1 muscarinic receptor probe. These results demonstrate that NGF specifically increases the transcription of genes (ChAT and m2 muscarinic receptor) the expression of which is associated with cholinergic neurons, promoting the growth of this particular type of neuron.