The increased opiate action of beta-endorphin in iron-deficient rats: the possible involvement of dopamine.
Rats made nutritionally iron-deficient (ID) have been shown to have a lower brain non-haem. A selective diminution of the binding capacity of the D2-dopaminergic receptors alone was found among nutritionally iron-deficient rats. Peripherally administered beta-endorphin significantly elevated the pain threshold only in the iron-deficient rats. Naloxone blocked the beta-endorphin effect in ID rats. Morphine, as well as haloperidol, elevated the pain threshold in both the iron-deficient and the control rats but significantly more in the former group. No additive effects of combined treatment with beta-endorphin and haloperidol on pain threshold were found. Other neuroleptics also elevated the pain threshold. A possible hypothesis is that dopamine (via beta-endorphin) may play a role in modifying the pain threshold.
D000818:Animals; D001812:Blood-Brain Barrier; D002940:Circadian Rhythm; D004298:Dopamine / Q000502:physiology*; D004723:Endorphins / Q000494:pharmacology*; D006220:Haloperidol / Q000494:pharmacology; D000090463:Iron Deficiencies; D008297:Male; D009020:Morphine / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects; D012684:Sensory Thresholds / Q000187:drug effects; D001615:beta-Endorphin
D004723:Endorphins; D011954:Receptors, Dopamine; D001615:beta-Endorphin; D009020:Morphine; D006220:Haloperidol; D004298:Dopamine