Reduction of NMDA-induced Ca2+ transients by a mu-opioid receptor agonist in dorsal horn neurons.
The effect of DAMGO, a mu-opioid receptor agonist, on intracellular Ca2+ transients evoked by the application of NMDA, was studied in freshly dissociated neurons from the superficial dorsal horn in the spinal cord of young rats. DAMGO (5-10 microns) reduced the amplitude of the Ca2+ transients measured with Fura-2 to 58 +/- 17% of the controls in 41% of the neurons tested. The effect of DAMGO was dose dependent and reversible. The reduction of NMDA-induced Ca2+ transients by DAMGO was prevented by application of the opioid antagonists naloxone (0.1-5 microM) and CTAP (0.2-2 microM). DAMGO also reduced Ca2+ transients induced by high K+ in 29% of the neurons. These data suggest that mu-receptor activation regulates NMDA-induced Ca2+ transients in a complex manner, by reducing both a depolarization-induced component and the NMDA-channel component of this Ca2+ signal.
Hocherman
S D
SD
Department of Veterinary Physiology and Pharmacology, Iowa State University, Ames 50011, USA.
Randić
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D010446:Peptide Fragments; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists*; D013004:Somatostatin; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
C529311:CTAP octapeptide; D004745:Enkephalins; D009292:Narcotic Antagonists; D010446:Peptide Fragments; D010455:Peptides; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009270:Naloxone; D013004:Somatostatin; D002118:Calcium