DPDPE antinociception

Delta receptors nevertheless mediate some delta agonist induced analgesia, as suggested by reduced DPDPE and deltorphin activity in the DOR mutant after ITH applications [52], or enhanced antinociceptive activity in MOR mutants subjected to CFA inflammation [65]. Delta receptors also depress respiratory neurons in slice preparations [66] and mediate SNC80-evoked convulsions [67]. 

Supraspinal DPDPE/ [D-Ala2]-delt II ai3, ai2 Antinociception Antisera 58,59... 

Spinal DPDPE aii, ori2, ori3, ao, as, aq, az Antinociception Antisense 59... 

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... 

There is considerable evidence that 5r and 2-opioid receptors act at supraspinal sites to modulate nociceptive responses. Direct ICV injection of the putative 5-opioid agonists DPDPE or DPLPE in the mouse produced dose-dependent antinociception that was blocked by ICI 174,864 but not by (5-FNA [87,88]. Furthermore, 5-opioid selective doses of DPDPE given ICV blocked nociception, but not gastrointestinal transit, in mice [99].The ICV administration of DPDPE has been shown to produce dose-dependent antinociception against mechanical nociception (Randall-Selitto paw with-... 

The spinal antinociceptive effect of DPDPE is blocked totally by a small conductance Ca2 + -activated K + channel blocker apamin [109]. The DPDPE-induced spinal antinociception is not inhibited by a ATP-sensitive K + channel blocker glyburide [109], Like morphine, tetraethylammonium, 4-aminopyridine, and charybdotoxin are unable to block the effects of DPDPE [109], These findings suggest that the modulation of apamin-sensitive K + channels appears to play a role in the DPDPE-induced antinociception in the spinal cord. 

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