Interaction between CCK and opioids in the modulation of the rectocolonic inhibitory reflex in rats.
The effects of cholecystokinin octapeptide (CCK-8) as well as the involvement of opioid system were evaluated in rectal distension (RD)-induced colonic motor inhibition in rats. Rats were surgically prepared with electrodes implanted on the proximal colon, and a catheter was implanted in lateral ventricle of the brain. RD was performed by inflation (0.0-1.6 ml) of a balloon rectally inserted. RD 1.6 ml of induced an inhibition of the colonic spike bursts (3.1 +/- 0.5 per 5 min vs. 8.1 +/- 0.4 before RD). Intracerebroventricular but not intravenous injection of CCK-8 and A-71623 (50 and 100 ng/kg) reduced the RD-induced colonic motor inhibition, whereas A-63387 was ineffective. PD-135,158 (10 micrograms/kg icv) suppressed the inhibitory reflex caused by RD. Devazepide (100 micrograms/kg icv) had no effect in this reflex function. Devazepide (1 microgram/kg), naloxone (0.1 mg/kg), and nor-binaltorphimine (nor-BNI; 10 mg/kg) reversed the blocking effect of CCK-8, whereas PD-135,158 (0.1 microgram/kg) and naltrindole (1 mg/kg) have no effect. In conclusion, CCK-8 acts on central alimentary cholecystokinin receptors to modulate the RD-induced inhibition of colonic motility through pathways involving activation of endogenous kappa-receptors.
Gué
M
M
Department of Pharmacology, Institute National de la Recherche Agronomique, Toulouse, France.
del Rio
C
C
Junien
J L
JL
Buéno
L
L
D000818:Animals; D002404:Catheterization; D002766:Cholecystokinin / Q000502:physiology*; D003106:Colon / Q000502:physiology*; D004347:Drug Interactions; D004723:Endorphins / Q000502:physiology*; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011949:Receptors, Cholecystokinin / Q000819:agonists / Q000502:physiology; D011957:Receptors, Opioid / Q000502:physiology; D012007:Rectum / Q000502:physiology*; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D012844:Sincalide / Q000494:pharmacology
D004723:Endorphins; D009292:Narcotic Antagonists; D011949:Receptors, Cholecystokinin; D011957:Receptors, Opioid; D002766:Cholecystokinin; D012844:Sincalide