CCK2 receptors mediate inhibitory effects of cholecystokinin on the motor activity of guinea-pig distal colon.
Cholecystokinin and related peptides are involved in the control of intestinal motility and cholecystokinin receptor ligands might represent new pharmacological tools for the treatment of symptoms associated with functional bowel disorders. However, the respective roles played by cholecystokinin receptor subtypes and the mechanisms underlying these regulatory actions remain undetermined. This study was designed to examine the influence of cholecystokinin receptor subtypes on the motor activity of guinea-pig distal colon. The effects of drugs acting on CCK1 and CCK2 receptors were assessed in vitro on the contractile activity of longitudinal smooth muscle, both under basal conditions and in the presence of transmural electrical stimulation or KCl-induced contractions. The application of cholecystokinin octapeptide sulphate (cholecystokinin-8S) to colonic preparations induced concentration-dependent contractions which were prevented by devazepide (CCK1 receptor antagonist), enhanced by GV150013 (CCK2 receptor antagonist) or N(omega)-nitro-L-arginine methylester (L-NAME, nitric oxide synthase inhibitor), and unaffected by tetrodotoxin. The application of gastrin-17 to colonic preparations resulted in relaxant responses which were insensitive to devazepide, and prevented by GV150013, L-NAME or tetrodotoxin. L-NAME, N(omega)-propyl-L-arginine (NPA, neuronal nitric oxide synthase inhibitor) or GV150013 enhanced electrically evoked contractile responses, whereas devazepide did not. When tested in the presence of L-NAME or NPA the enhancing effect of GV150013 on electrically induced contractions no longer occurred. In the presence of KCl-induced pre-contractions, cholecystokinin-8S or gastrin-17 evoked concentration-dependent relaxations, which were unaffected by devazepide and were counteracted by GV150013, L-NAME, NPA or tetrodotoxin. In conclusion, the present results indicate that, at level of distal colon, CCK1 receptors mediate direct contractile effects on smooth muscle, whereas CCK2 receptors on enteric neurons mediate relaxant responses via nitric oxide release.
Fornai
Matteo
M
Division of Pharmacology and Chemotherapy, Department of Internal Medicine, University of Pisa, Via Roma, 55, 56126 Pisa, Italy.
Colucci
Rocchina
R
Antonioli
Luca
L
Baschiera
Fabio
F
Ghisu
Narcisa
N
Tuccori
Marco
M
Gori
Giovanni
G
Blandizzi
Corrado
C
Del Tacca
Mario
M
D000218:Adamantane / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002766:Cholecystokinin / Q000494:pharmacology*; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D020109:Devazepide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005755:Gastrins / Q000494:pharmacology; D006168:Guinea Pigs; D006727:Hormone Antagonists / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D052248:Nitric Oxide Synthase Type I / Q000494:pharmacology; D018697:Nootropic Agents / Q000494:pharmacology; D010477:Perfusion; D010671:Phenylurea Compounds / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D043887:Receptor, Cholecystokinin B / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology
C090019:8-sulfocholecystokinin octapeptide; D004338:Drug Combinations; D004791:Enzyme Inhibitors; C111554:GV 150013X; D005755:Gastrins; D006727:Hormone Antagonists; D018697:Nootropic Agents; D010671:Phenylurea Compounds; D043887:Receptor, Cholecystokinin B; C013550:gastrin 17; D011189:Potassium Chloride; D002766:Cholecystokinin; D052248:Nitric Oxide Synthase Type I; D020109:Devazepide; D012844:Sincalide; D000218:Adamantane; D019331:NG-Nitroarginine Methyl Ester