Fig. 2.

Optoid binding in brain membrane preparations from adult rats treated in vivo with various concentrations of buprenorphine. Adult male rats were administered (intraperitoneally) either buprenorphine (0.5–2.5 mg/kg) or saline, and 20 hr later forebrains were collected. The affinity of [³H]DAMGE (μ) is shown in Fig. 3. In the order of increasing bupren­orphine concentrations from 0 to 2.5 mg/kg, K_d values were 2.2 ± 0.2, 2.0 ± 0.3, 2.2 ± 0.3, and 4.6 ± 0.6 nM ([³H]DSLET); 2.0 ± 0.2, 2.0 ± 0.3, 2.4 ± 0.2, and 1.6 ± 0.3 nM ([³H]DPDPE); and 3.3 ± 0.6,6.2 ± 1.2, 4.3 ± 0.5, and 5.7 ± 1.5 nM ([³H]U69593. *, Significantly different from saline-treated, p < 0.05. Results are from three to six separate experiments.