TABLE 1

Summary of results

I-ME (pA), The mean amplitude of the currents induced by [Met5]-enkephalin (ME) (0.3 and 30 µM) in slices from wild-type animals (WT) and each of the mutant μ-opioid receptor (MORs). There was no statistical difference from WT (ANOVA, Dunnett’s post hoc), indicating that the sensitivity to ME in slices from WT animals was similar to slices taken from animals expressing each of the mutant receptors. Decline (10 min/peak): Paired comparison between experiments from untreated and morphin-treated animals (MTAs) showing the decrease in current induced by ME (30 µM) during a 10-minute application for each of the mutant receptors. In slices from animals expressing the TSST-4E receptors, the decline was increased in MTAs, P < 0.05, upaired t test). ME (0.3, post/pre): Paired comparison between slices from untreated and MTAs. The ratio of the current induced by ME (0.3 µM) after desensitization normalized to the initial current for each of the mutant receptors. This ratio decreased in WT, STANT-7A, and TSST-4E (P < 0.05, unpaired t test).

I- ME (pA)Decline (10 min/Peak)ME (0.3 µM), Post/Pre
0.3 µM30 µMUntreatedMTAUntreatedMTA
WT279 ± 96 (7)451 ± 95 (7)0.60 ± 0.16 (7)0.51 ± 0.07 (9)0.23 ± 0.06 (7)0.13 ± 0.08 (9)
STANT-3A259 ± 137 (9)439 ± 134 (9)0.79 ± 0.07 (7)0.78 ± 0.08 (7)0.62 ± 0.14 (10)0.56 ± 0.15 (9)
STANT-7A290 ± 138 (8)435 ± 143 (8)0.73 ± 0.10 (9)0.83 ± 0.09 (14)0.82 ± 0.15 (9)0.61 ± 0.13 (13)
TSST-4A231 ± 82 (8)425 ± 123 (8)0.53 ± 0.13 (7)0.60 ± 0.05 (10)0.25 ± 0.14 (6)0.33 ± 0.11 (5)
TSST-4E286 ± 102 (7)400 ± 123 (10)0.65 ± 0.10 (7)0.49 ± 0.13 (10)0.41 ± 0.12 (7)0.18 ± 0.13 (10)