Up-regulation of [3H]DAMGO and [3H]DTLET opioid binding sites in laminae I-II of the spinal cord in intact and deafferented morphine-tolerant rats.
Using quantitative autoradiography and selective opioid ligands, we have measured the effects of morphine-induced tolerance on [3H]DAMGO and [3H]DTLET binding sites in the superficial spinal dorsal horn (laminae I-II) of intact and deafferented rats (unilateral C4-T2 dorsal rhizotomy). In intact rats, the treatment induced an up-regulation of 26% and 39% for [3H]DAMGO and [3H]DTLET binding sites, respectively, without modification of receptor affinity. In deafferented rats, the treatment similarly induced an up-regulation of 31% and 29% for [3H]DAMGO and [3H]DTLET binding sites, respectively, on the contralateral side, and of 21% and 25%, respectively, on the ipsilateral side. These data demonstrate that the up-regulation induced by morphine tolerance is of similar magnitude for both presynaptic (on primary afferent fibers) and postsynaptic (on spinal neurons) opioid binding sites in the rat dorsal horn.
Besse
D
D
Unité de Recherche de Physiopharmacologie du Système Nerveux, INSERM, U. 161, Paris, France.
Lombard
M C
MC
Besson
J M
JM
D000818:Animals; D001345:Autoradiography; D004361:Drug Tolerance; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000378:metabolism*; D009020:Morphine / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides / Q000378:metabolism*; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology*
D004745:Enkephalins; D009842:Oligopeptides; D011957:Receptors, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009020:Morphine; C037653:deltakephalin