Differences of mu-opioid receptors between Lewis and F344 rats.
F344 and Lewis rats show different responses to opioids in several experimental paradigms. In this study we have used the specific mu-opioid agonist DAMGO to find out if these differences could be attributed to heterogeneity of mu-opioid receptors. The density of [H3]DAMGO binding sites was similar in the brain cortex and spinal cord of both strains, but DAMGO affinity for mu-opioid receptors was higher in F344 tissues. Moreover, a parallel study of the effects of DAMGO on electrically-evoked twitches of isolated vasa deferentia revealed that this drug was also more effective in F344 preparations. These results suggest that mu-opioid receptors of F344 rats are more sensitive to pharmacological stimulation in vitro, which could be related to a higher drug affinity.
Herradón
G
G
Laboratory of Pharmacology, San Pablo CEU University, 28668 Boadilla, Madrid, Spain.
Morales
L
L
Alguacil
L F
LF
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D004558:Electric Stimulation; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D011917:Rats, Inbred Lew; D017465:Receptors, Opioid, delta / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism
D000701:Analgesics, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-