Effect of CCK-B receptor antagonist on [Ca~(2+)]i, CaM activity and CaMK II α expression in hippocampal neurons during naloxone-precipitated withdrawal in morphine-dependent rats

Abstract

Objective To investigate the effect of CCK-B receptor antagonist CR-2945 on cytoplasmic free calcium concentration ([Ca~(2+)]i), calmodulin (CaM) activity and calmodulin-dependent protein kinase Ⅱα(CaMK Ⅱα) expression in hippocampal neurons during naloxone-precipitated withdrawal in morphine-dependent rats. Methods Forty-five adult male Wistar rats weighing 180-240 g were randomly divided into 9 groups ( n = 5 each):morphine dependence group ( group MD) , normal saline group ( group NS), naloxone-precipitated withdrawal group ( group NPW ) , nucleus accumbens group ( group NA ) , amygdale group ( group A), lateral cerebral ventricle group (group LCV) , abdominal cavity (acute) group (group AC A) , abdominal cavity (chronic) group (group ACC) and placebo group (group P). Morphine dependence was induced by increasing doses of subcutaneous injection of morphine for 5 d and subcutaneous injection of morphine 50 mg/kg at 8:00 on 6th day. In group NS, equal volume of normal saline was injected instead of morphine. In group NPW, intraperitoneal nalxone 5 mg/kg was injected 1 h after the last subcutaneous injection of morphine. In group NA, A and LCV, CR-2945 10μg was injected into nucleus accumbens, amygdale and lateral ventricle 1 h after the last subcutaneous injection of morphine, and then intraperitoneal naloxone 5 mg/kg was injected 30 min later. In group ACA, CR-2945 1 mg/kg was injected 1 h after the last subcutaneous injection of morphine, and then intraperitoneal naloxone 5 mg/kg was injected 30 min later. In group ACC, CR-2945 1 mg/kg was injected simultaneously with morphine injection for 6 d, and intraperitoneal naloxone 5 mg/kg was injected 30 min after the last administration. In group P, normal saline was used instead of CR-2945, and the other procedures were the same as those in group LCV. Rats were killed and hippocampus was isolated. [Ca~(2+)]i and CaM activity were measured by flow cytometry. CaMK Ⅱα expression was determined by Western blot. Results [Ca~(2+) ]i, and CaM activity were significantly increased and CaMK Ⅱα expression was up-regulated in group MD compared with group NS (P 0.05) . Conclusion CCK-B receptor antagonist CR-2945 can inhibit naloxone-precipitated withdrawal responses through increasing [Ca~(2+)]i and CaM activity and up-regulating CaMK Ⅱα expression in hippocampal neurons in morphine-dependent rats. Key words: Receptor; cholecystokinin B; Morphine dependence; Naloxone; Substance withdrawal syndrome; Hippocampus; Neurons; Calcium; Calmodulin; Calcium-calmodulin-dependent protein kinase type 2