Tolerance DPDPE

Another important consideration promoting the view that subtypes of the 6-opioid receptor exist is the remarkable lack of cross-tolerance between agonists at the and 2 opioid receptors. Furthermore, no cross-tolerance exists between 5 -and p-opioid receptors [33,38,44,45]. In one of the earliest studies, acute tolerance to spinal DPDPE or to DSLET was elicited in (3-FNA-pretreated (i.e., p receptors blocked) mice [45]. Pretreatment with DPDPE attenuated the antinociceptive effect of subsequent spinal DPDPE but not that of DSLET, whereas pretreatment with DSLET attenuated the effect of DSLET and not DPDPE [45]. A similar lack of cross-tolerance... 

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