In vitro and ex vivo effects of a selective nociceptin/orphanin FQ (N/OFQ) peptide receptor antagonist, CompB, on specific binding of [3H]N/OFQ and [35S]GTPgammaS in rat brain and spinal cord.
1. A novel selective nociceptin/orphanin FQ (N/OFQ) peptide receptor antagonist, 1-[(3R,4R)-1-cyclooctylmethyl]-3-hydroxymethyl-4-piperidyl)-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (CompB), inhibited specific binding of [(3)H]N/OFQ to crude membranes from the rat brain and spinal cord in a concentration-dependent manner and their K(i) values were 7.11 and 4.02 nM, respectively. Rosenthal analysis indicated that there was a significant increase in the K(d) value for [(3)H]N/OFQ binding in the brain and spinal cord in the presence of CompB (10 nM). 2. There was a dose-dependent increase in K(d) values for [(3)H]N/OFQ binding in the brain and spinal cord following i.v. injection of CompB at relatively low doses (0.69-6.88 micro mol kg(-1)), compared with the control values. In the spinal cord, enhancement with each dose was constantly greater and the duration of enhancement (6.88 micro mol kg(-1)) was significantly longer. 3. The degree of increase in K(d) values for [(3)H]N/OFQ binding after i.v. injection of CompB (6.88 micro mol kg(-1)) was significantly larger in the lumbar region of the spinal cord compared to other regions. 4. CompB (0.1, 0.3 micro M) shifted the concentration-effect curves of N/OFQ-stimulated [(35)S]GTPgammaS binding in the brain and spinal cord to the right. 5. The i.v. injection of CompB (6.88 micro mol kg(-1)) significantly suppressed the N/OFQ-stimulated [(35)S]GTPgammaS binding in the rat spinal cord and shifted the concentration-effect curve to the right, while it produced little inhibitory effect in the brain. The present study has shown that CompB may exhibit pharmacological effects through a predominant blockade of N/OFQ peptide receptors in the spinal cord under in vivo conditions.
Yamada
Shizuo
S
Department of Biopharmacy, School of Pharmaceutical Sciences & COE21, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. yamada@ys7.u-shzuoka-ken.ac.jp
Kusaka
Toyofumi
T
Urayama
Akihiko
A
Kimura
Ryohei
R
Watanabe
Yasuo
Y
D000818:Animals; D001562:Benzimidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007275:Injections, Intravenous; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists; D018847:Opioid Peptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects* / Q000378:metabolism; D000094942:Nociceptin Receptor
D001562:Benzimidazoles; D006160:Guanosine Triphosphate; D009271:Naltrexone; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D010446:Peptide Fragments; D010880:Piperidines; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; C402921:J 113397; C051843:binaltorphimine; C055382:naltrindole; C000722285:Oprl1 protein, rat