TABLE 9.
Effects of sodium on inhibition of opioid agonists and antagonists of stereospecific [3H]naloxone binding in rat brain homogenates
The IC50 values for the designated competitor against [3H]naloxone binding in the absence (Control) and presence of sodium chloride (100 mM) were determined. The sodium shift was calculated as the ratio of the IC50 values in the presence and absence of sodium chloride (IC50 sodium chloride/IC50 control). Modified from Pert et al. (1973).
| Competitor | Control | NaCl (100 mM) | Sodium Shift |
|---|---|---|---|
| Naloxone | 1.5 | 1.5 | 1 |
| Naltrexone | 0.5 | 0.5 | 1 |
| Diprenorphine | 0.g | 0.g | 1 |
| Cyclazocine | 0.9 | 1.5 | 1.7 |
| Levallorphan | 1 | 2 | 2 |
| Nalorphine | 1.5 | 4 | 2.7 |
| Pentazocine | 15 | 50 | 3.3 |
| Etorphine | 0.5 | 6 | 12 |
| Meperidine | 3,000 | 50,000 | 17 |
| Levorphanol | 1 | 15 | 15 |
| Oxymorphone | 1 | 30 | 30 |
| Dihydromorphine | 3 | 140 | 47 |
| Propoxyphene | 200 | 12,000 | 60 |
| Phenazocine | 0.6 | 80 | 133 |