Regulation of cyclic AMP by the mu-opioid receptor in human neuroblastoma SH-SY5Y cells.
The human neuroblastoma clonal cell line SH-SY5Y expresses both mu- and delta-opioid receptors (ratio approximately 4.5:1). Differentiation with retinoic acid (RA) was previously shown to enhance the inhibition of adenylyl cyclase (AC) by mu-opioid agonists. We tested here the inhibition of cyclic AMP (cAMP) accumulation by morphine under a variety of conditions: after stimulation with prostaglandin E1 (PGE1), forskolin, and vasoactive intestinal peptide (VIP), both in the presence and in the absence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Morphine inhibition of the forskolin cAMP response (approximately 65%) was largely unaffected by the presence of IBMX. In contrast, deletion of IBMX enhanced morphine's inhibition of the PGE1 and VIP cAMP response from approximately 50 to approximately 80%. The use of highly mu- and delta-selective agents confirmed previous results that inhibition of cAMP accumulation by opioids is mostly mu, and not delta, receptor mediated in SH-SY5Y cells, regardless of the presence or absence of IBMX. Because of the large morphine inhibition and the high cAMP levels even in the absence of IBMX, PGE1-stimulated, RA-differentiated SH-SY5Y cells were subsequently used to study narcotic analgesic tolerance and dependence in vitro. Upon pretreatment with morphine over greater than or equal to 12 h, a fourfold shift of the PGE1-morphine dose-response curve was observed, whether or not IBMX was added. However, mu-opioid receptor number and affinity to the mu-selective [D-Ala2, N-Me-Phe4, Gly5-ol]enkephalin were largely unaffected, and Na(+)- and guanyl nucleotide-induced shifts of morphine-[3H]naloxone competition curves were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
Yu
V C
VC
Department of Pharmacy, University of California, San Francisco 94143-0446.
Eiger
S
S
Duan
D S
DS
Lameh
J
J
Sadée
W
W
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D000527:Alprostadil / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009020:Morphine / Q000494:pharmacology; D009447:Neuroblastoma; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D013806:Theophylline / Q000031:analogs & derivatives*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D004745:Enkephalins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D005576:Colforsin; D014660:Vasoactive Intestinal Peptide; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-; D013806:Theophylline; D000242:Cyclic AMP; D000527:Alprostadil; D015056:1-Methyl-3-isobutylxanthine