Developmental change of mu opioid receptors in neonatal guinea pig brain stem.
Opioid receptor binding of morphine-6-beta-D-glucuronide (M6G), morphine and [3H][D-Ala2,N-methylPhe4-Glyol5]enkephalin (DAMGO) were determined in neonatal guinea pigs. Pontomedullary membranes specifically bound [3H]DAMGO, which was displaced by M6G and morphine. The KI for M6G and morphine were 15.1 nM and 5.0 nM, respectively, and did not change between day 3 and day 7 after birth. KD for [3H]DAMGO binding was constant (1.1nM), however Bmax increased from 62.2 to 88.3 fmol/mg protein between days 3 and 7 (P < 0.01). This 42% increase in mu receptors may play a role in the increased potency of M6G respiratory effects for guinea pigs during the first week after birth.
Murphey
L J
LJ
Department of Pharmacology, School of Medicine, Oregon Health Sciences University, Portland 97201-3098, USA.
Olsen
G D
GD
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism*; D001933:Brain Stem / Q000378:metabolism*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D006168:Guinea Pigs / Q000254:growth & development / Q000378:metabolism*; D009020:Morphine / Q000494:pharmacology; D009022:Morphine Derivatives / Q000494:pharmacology; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000378:metabolism*
D004745:Enkephalins; D009022:Morphine Derivatives; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C035349:morphine-6-glucuronide; D009020:Morphine; C018108:morphine-3-glucuronide