Fig. 1.

A deficiency of δ receptors causes a reduction in μ-receptor inhibitory coupling to VDCCs. A, exemplar superimposed Ca²⁺ currents evoked by depolarizing δ(+/+) and δ(-/-) DRG neurons from -80 to 0 mV, recorded in the absence and presence of DAMGO (1 μM). B, bar graph indicating the mean Ca²⁺ current inhibition by μ, δ, and GABA_B receptor-selective agonists, DAMGO (1 μM), morphine (1 μM), DPDPE (1 μM), and baclofen (50 μM). Data points are averages of between 5 and 22 recordings. Vertical lines represent ± S.E.M. ANOVA with a post hoc Scheffe test was used to determine the statistical significance, across genotypes, of differences in the mean inhibitions: ^*, p < 0.05; ^**, p < 0.01; ^***, p < 0.001.