THE EFFECT OF NALTRINDOLE ON DELTA-OPIOID RECEPTOR-BINDING AND FUNCTIONAL-EFFECTS IN THE MOUSE

Accumulated evidence strongly suggests that there are subtypes of delt a opioid receptors. Naltrindole (NTI) is a nonpeptide delta opioid rec eptor antagonist (e.g., 1) that has been shown to have high selectivit y in binding studies for delta receptors compared to kappa and mu (1,2 ). In functional studies, NTI selectively blocks delta opioid agonists (e.g., 3,4). However, NTI appears to favor the delta(2) site over the delta(1) site (5). In the present study we examined the relationship between the functional effects of NTI and its effects on delta(1) and delta(2) receptors, In this report we demonstrate that changes in bind ing of [H-3]DSLET and [H-3]DPDPE in mouse brain and spinal cord follow ing NTI are not closely tied to observed changes in the analgesic pote ncy of spinal and supraspinal administration of the same agonists in t he mouse.