Effect of low pH treatment on opioid peptides binding to their receptors and functional coupling of G-proteins to adenylyl cyclase in the rat spinal cord.
Because low pH treatment is known to alter the coupling of G-proteins to brain receptors, and little is known about such an effect in the spinal cord, the present study was undertaken to examine whether preincubation of rat spinal cord membranes at low pH (pH 4.5) alters opioid receptor binding characteristics and sodium fluoride (NaF)-stimulated adenylyl cyclase (AC) activity (as a function of G, mediated). [3H][D-Ala2,MePhe4,Gly-ol]enkephalin (DAMGO) and [3H]ethylketocyclazosine (EKC) were used to label mu- and kappa-opioid receptors, respectively. AC activity was determined using ATP as substrate and cAMP formed was quantified. Low pH treatment of membranes did not affect the mu- and kappa-opioid binding characteristics in rat spinal cord. However, the low pH treatment significantly reduced the NaF-stimulated AC activity in rat spinal cord. It is concluded that low pH treatment causes selective changes in the functional coupling of Gs-proteins to AC without affecting the opioid receptor binding characteristics in the spinal cord.
Reddy
P L
PL
Department of Pharmaceutics and Pharmacodynamics (M/C 865), University of Illinois at Chicago 60612, USA.
Bhargava
H N
HN
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000700:Analgesics / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000378:metabolism*; D016314:Ethylketocyclazocine / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D013116:Spinal Cord / Q000378:metabolism*
D000700:Analgesics; D004745:Enkephalins; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D016314:Ethylketocyclazocine; D012969:Sodium Fluoride; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases