Relation of diltiazem binding sites to opioid receptor subtypes in the guinea-pig brain.
Interactions between diltiazem and opioids in guinea-pig brain membrane preparations were examined. Diltiazem did not inhibit bindings of 3H-dihydromorphine (3H-DHM), 3H-ethylketocyclazocine (3H-EKCZ) and 3H-naloxone (3H-NOX) but inhibited binding of 3H-[D-Ala2, D-Leu5]-enkephalin (3H-DADLE). In 3H-DADLE binding, diltiazem decreased the reciprocal indices of affinity (Kd values) of 3H-DADLE without changing on the maximal saturable binding (B. max) in guinea-pig brain membranes. These effects of diltiazem on the binding of 3H-DADLE were enhanced by 2.5mM CaCl2. Morphine, EKCZ, naloxone and even DADLE did not change the binding of 3H-diltiazem. These results suggest that the current of information concerning diltiazem and DADLE binding sites is one-way only so that no interaction exists.
Ishizuka
Y
Y
Department of Pharmacology, School of Medicine, Tokai University, Japan.
Oka
T
T
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D003496:Cyclazocine / Q000031:analogs & derivatives / Q000378:metabolism; D004090:Dihydromorphine / Q000378:metabolism; D004110:Diltiazem / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine; D016314:Ethylketocyclazocine; D006168:Guinea Pigs; D009270:Naloxone / Q000378:metabolism; D011869:Radioligand Assay; D011957:Receptors, Opioid / Q000378:metabolism*
D011957:Receptors, Opioid; D009270:Naloxone; D016314:Ethylketocyclazocine; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D004090:Dihydromorphine; D004110:Diltiazem; D003496:Cyclazocine