EHT treatment attenuates MPTP-induced nigrostriatal dopaminergic neuronal damage. Mice were treated with EHT for 4 weeks and challenged with MPTP (10 mg/kg, every 2 h X4). Brains were analyzed 7 days post MPTP. a, b Stereological counting of TH-positive and cresyl-violet positive neurons in sections of the substantia nigra from one hemisphere. Normal diet-saline injections (control), n = 4; normal diet-MPTP, n = 3; EHT in diet (0.01 %)-MPTP, n = 4; and EHT in diet (0.1 %)-MPTP, n = 3. c Representative images of TH immunohistochemistry of midbrain sections. Scale bar = 200 μm. d Striatal dopamine (DA) level measured by HPLC. Control (no EHT or MPTP), n = 6; normal diet-MPTP, n = 5; EHT (0.01 %)-MPTP, n = 6; and EHT (0.1 %)-MPTP, n = 5. e Dopamine turnover measured by HVA/dopamine ratio. f Striatal TH content measured by ELISA. Control, n = 6; normal diet-MPTP, n = 5; EHT (0.01 %)-MPTP, n = 6; and EHT (0.1 %)-MPTP, n = 5. g EHT treatment had no impact on MPTP metabolism in vivo. Mice were treated with two dose levels of EHT for 2 weeks prior to receiving a single dose of 30 mg/kg MPTP. Animals were sacrificed 90 minutes later (n = 4 per group). MPP+ levels were assessed by HPLC. *p < 0.05, **p < 0.01, ***p < 0.001