Figure 4.

Extracellular μ-calpain selectively kills dopaminergic neurons. Rat mesencephalic neuron-glia cultures were treated with either medium alone (control), lipopolysaccharide (LPS; 10 ng/ml) or μ-Calpain (3.8 μg/ml, 1.9 μg/ml or boiled). (A) Loss of dopaminergic neuron function was measured 9 days later with the [³H] dopamine uptake assay. (B) Loss of dopaminergic neurons was determined 9 days later by counting the number of tyrosine hydroxylase (TH)-immunoreactive (IR) neurons. (C) Tyrosine hydroxylase staining demonstrates μ-calpain-induced morphological damage to dopaminergic neurons. The arrow denotes the damaged dopaminergic neuron and the scale bar indicates 50 μm. Representative images are from three separate experiments. (D) Dopamine neurotoxicity (DA) and GABA neurotoxicity (GABA) was determined 9 days later by [³H] dopamine or GABA uptake assay. (E) General loss of total neurons (NeuN-immunoreactive neurons) was determined 9 days later by the cell count. Graphs show the results expressed as percentage of the control cultures and are the mean ± SEM from three independent experiments in triplicate. *P < 0.05, control compared to treatment; ^#P < 0.05 indicates significant differences in selective neurotoxicity (tyrosine hydroxylase versus GABA).