AJP - Gastrointestinal and Liver Physiology, Vol 269, Issue 2 240-G245, Copyright © 1995 by American Physiological Society
Interaction between CCK and opioids in the modulation of the rectocolonic inhibitory reflex in rats
M. Gue, C. del Rio, J. L. Junien and L. Bueno
Department of Pharmacology, Institute National de la Recherche Agronomique, Toulouse, France.
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.
