[Cholecystokinin octapeptide antagonized the effect of NDAP on CaM in rat dorsal spinal synaptosome]

To elucidating the molecular mechanisms underlying CCK-8 anti-opioid effects, we have observed the effects and interactions of CCK-8 and kappa opiate agonist NDAP on CaM activity in rat dorsal spinal cord synaptosomes. The result indicated that 10 nmol/L-1 mumol/L NDAP produced dose-dependent decrease in CaM activity of rat spinal synaptosomes (P < 0.01). This suppressive effect was completely blocked by specific kappa receptor antagonist Nor-BNI at 1 mumol/L. In contrast, CCK-8 (10-100 nmol/L) induced a significant increase in CaM activity (P < 0.05-0.01), and was capable of antagonizing the suppressive effect induced by NDAP. Specific CCK-B receptor antagonist L365, 260 could partially block the effects of CCK-8 increased CaM activity at 1 mumol/L. The above results suggest that CCK-8 can antagonize the suppressive effect of NDAP on CaM activity in rat spinal synaptosomes via activation of CCK-B receptor, an effect that may constitute one of the mechanisms for the anti-opioid activity of CCK-8.