Effects of nano-ZnO and bulk ZnO on the expression of morphine-induced conditioned place preference in mice

Extracellular zinc ion is an important factor in regulation of opioids activity. However، little research on the effects of nanoscale zinc ion on opioids dependence has been done. So، the aim of this research was to compare the effects of zinc oxide nano particles and the bulk on the expression of morphine conditioned place preference (MCPP). In this study، 112 adult male mice weighing 25 ±3 grams in 16 groups (7 per group) was used. At first، different doses of morphine were given (2. 5، 5، 10 mg / kg، SC) to determine the effectiveness of drug-induced conditioned place preference by using the bias method. Secondly، different doses of the nano zinc oxide and bulk zinc oxide (2. 5، 5، 10mg /kg، IP) were administered to evaluate the expression of (MCPP). Morphine increased the spent time in place with receiving morphine as a dose dependent manner (CPP). The increases at dosage of 5 and 10 mg/kg morphine was significant (p <0. 001). Both nano and bulk zinc oxide could not induce place preference. Nano zinc oxide in all doses (p<0. 05، p<0. 001) and bulk-ZnO at dosage of 5 and 10 mg/kg (p<0. 001) decreased the expression of morphine-induced conditioned place preference، significantly. Therefore، nano zinc oxide is more potent than the bulk from for inhibition. It seems that nano zinc has more efficacy for inhibition of morphine dependence. This effect is probably due to better interaction with neurochemical systems which are involved in the process of opioid dependence.