Meptazinol is an interesting opioid-producing naloxone-reversible analgesia with few cardiovascular and respiratory effects. Recent studies indicate that mu1 opioid receptors mediate meptazinol analgesia. Using a computerized autoradiographic subtraction technique, we have examined the regional distribution of meptazinol-sensitive [3H][d-Ala2,MePhe4,Gly(ol)5]enkephalin (DAGO) binding and compared this with the distribution of mu1 binding determined by competition with low [d-Ala2,d-Leu5]enkephalin (DADL) concentrations.
Meptazinol and DADL lowered [3H]DAGO to similar extents in most brain regions studied. The greatest levels of inhibition were observed in the periaqueductal gray, interpeduncular nucleus, thalamus, hypothalamus, and hippocampus. Low levels of inhibition were found in the temporal and frontal cortex. The correlation between the inhibition of [3H]DAGO binding by meptazinol and that by DADL was high (r = 0.83), consistent with the binding of meptazinol to mu1 sites.
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Adler, B.A., Goodman, R.R. & Pasternak, G.W. Quantitative autoradiographic distribution of meptazinol-sensitive binding sites in rat brain. Cell Mol Neurobiol 8, 471–476 (1988). https://doi.org/10.1007/BF00711230
- opiate receptor
- mu1 receptor