Lack of interaction between methionine enkephalin and D-phenylalanine on nociceptive and non-nociceptive responses of dorsal horn neurones of the cat.
In the spinal cord of the barbiturate anaesthetized cat, D-phenylalanine (DPA) depressed spontaneous and amino acid-induced firing of multireceptive dorsal horn neurones. The excitation of these neurones by noxious and non-noxious cutaneous stimuli was non-selectively depressed by DPA. DPA did not potentiate the depressant action of methionine enkephalin on these cells. Although naloxone reduced the depressant action of DPA, this was associated with increases in spontaneous firing. Spinal reflexes in this preparation are tonically inhibited by opioid peptides. Intravenous DPA (20-70 mg/kg) did not potentiate this inhibition but produced small increases in spinal reflexes. Collectively these data do not support the hypothesis that analgesia from DPA results from potentiation of endogenously released methionine enkephalin.
D000698:Analgesia; D000818:Animals; D002415:Cats; D004347:Drug Interactions; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D010649:Phenylalanine / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects; D012018:Reflex; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D011957:Receptors, Opioid; D009270:Naloxone; D010649:Phenylalanine; D004744:Enkephalin, Methionine