Functional Crosstalk between CB and TRPV1 Receptors Protects Nigrostriatal Dopaminergic Neurons in the MPTP Model of Parkinson’s Disease
The CB receptor is associated with TRPV1-activated neuroprotection in the SN of MPTP-treated mice in vivo. (a) Diagram of the experimental design. Mice were intraperitoneally given an injection of PBS or MPTP. All mice intraperitoneally received PBS as a control or cannabinoid (CB) antagonist (AM251 (A2) or AM630 (A6); 0.1 mg/kg/day) for 7 days at 30 min before capsaicin (C) and 1 hour before MPTP and a single injection of capsaicin (0.5 mg/kg) at 30 min before MPTP. Mice that received PBS as a control (CON); capsaicin (C); MPTP (M); MPTP and capsaicin (MC); MPTP, capsaicin, and AM251 (MCA2); or MPTP, capsaicin, and AM630 (MCA6) were sacrificed at 7 days after the last MPTP injection. Brains were removed, and coronal sections (30 μm) were cut using a sliding microtome. Every sixth serial section was selected and processed for TH immunohistochemical staining. (b) Photomicrographs of TH+ neurons in the SN. Higher magnification of each group for TH staining, respectively. These data are representative of five to six animals per group. (c) TH+ neurons were counted using a stereological technique in the SN. Bars represent the of five to six animals per group. , significantly different from control. &, significantly different from MPTP. #, significantly different from MPTP and capsaicin (one-way ANOVA with the Neuman-Keuls post hoc test). SNpc: substantia nigra pars compacta; SNr: substantia nigra pars reticulata; VTA: ventral tegmental area. Scale bars: 250 μm (left panel for (b)). Scale bars: 50 μm (right panel for (b)).