Data Analysis

Data were compiled and analyzed in Prism 8 (GraphPad Software, La Jolla, CA, USA) and presented as means ± standard error. Linear regressions were performed on total plasma and unbound brain concentrations to interpolate unbound brain concentration relative to clinically relevant plasma concentrations of samidorphan (46.1 ng/mL) and naltrexone (16.1 ng/mL). Percent receptor occupancy was also expressed as a function of unbound brain concentration and as a 4-parameter nonlinear regression curve fit with upper and lower bounds not constrained. Hill slope for DOR and KOR curves were constrained to 1 as the curve did not reach linearity. The half-maximal effective concentration (EC₅₀) values (where possible) and occupancy at the calculated clinically relevant brain concentrations were interpolated using these curve fits.