Effect of prolonged administration of clonidine on [3H]PN 200-110 and [125I]omega-conotoxin binding in mouse brain.
The effect of chronic exposure to clonidine or morphine on clonidine- and morphine-induced analgesia in mice was examined. Binding of L- or N-type calcium channel antagonist to cortical membrane fractions was also compared between these groups of mice. A decrease in the analgesic effect of clonidine and morphine was observed following prolonged administration of clonidine or morphine. Binding of [3H]PN 200-110, an L-type calcium channel antagonist, decreased following prolonged administration of clonidine whereas it increased after morphine treatment. On the other hand, a significant increase of [125I]omega-conotoxin, an N-type calcium channel antagonist, binding was observed after chronic clonidine or morphine treatment. These results will be discussed in relation with the possible development of cross-tolerance between clonidine and morphine through the change in calcium channels, more specifically in N-type channels.
Suematsu
M
M
Second Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Osaka University, Suita, Japan.
Ohnishi
T
T
Shinno
E
E
Maeda
S
S
Matsumoto
K
K
Sakuda
M
M
Saito
K
K
D000818:Animals; D002121:Calcium Channel Blockers / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology*; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D007457:Iodine Radioisotopes; D017275:Isradipine / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects; D010455:Peptides / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007457:Iodine Radioisotopes; D010455:Peptides; D020960:omega-Conotoxins; D014316:Tritium; C053423:Conus magus toxin; D009020:Morphine; D003000:Clonidine; D017275:Isradipine