Expression of the μ, κ, and δ-opioid receptors and tyrosine hydroxylase in MN9D cells.

Dopaminergic neurons are suggested to be a critical physiopathology substrate for addiction disorders. It is not well known whether the clonal mesencephalic dopaminergic cell line MN9D cells can be applied to study morphine addiction. Immunofluorescence staining and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect protein and mRNA expression of the μ, κ, and δ-opioid receptors in MN9D cells. Immunofluorescence staining of TH was applied to quantify the number of dopaminergic neurons. The results showed that the μ, κ, and δ-receptors were all expressed in MN9D cells, and the number of TH-positive cells was significantly greater in the MN9D cells than SH-SY5Y cells. The data suggest that MN9D cells can be used as an in vitro models in future studies to explore the mechanisms of morphine addiction related to dopaminergic neurons.