Effect of Intra CA1 and Intraperitoneal Administration of Opioid Receptor Modulating Agents on The Anxiolytic Properties of Nano and Conventional ZnO in Male Rats

Objective: Nano components are today’s new wonder material. However, the safety or toxicity of these components in humans is not yet clear. In a previous study we indicated that nano ZnO (nZnO) has a stronger anxiolytic effect compared to the conventional ZnO (cZnO). The present study was designed to evaluate the intraperitoneal administration of an opioidergic receptor agonist and antagonist of as well as the intra CA1 administration of an opioidergic receptor antagonist on the anxiolytic properties of nano and conventional ZnO in adult male Wistar rats. Materials and Methods: In this experimental study, rats received drugs via two modes of injection; intraperitoneal (IP.) and intra CA1 (intra hippocampus, CA1 area). Firstly, nZnO (5, 10, 20 mg/kg), cZnO (5, 10, 20 mg/kg), morphine 6 mg/kg, and naloxone 1 mg/kg were injected IP and naloxone 1?g/rat was injected intra CA1. Subsequently, morphine and naloxone (IP and intra CA1) were co-injected with the effective dose of nZnO and cZnO. An elevated plus maze was used to evaluate anxiety related behavior and anxiety parameters 30 minutes after the second injection. Results: The results indicated that the anxiolytic effects of nZnO 5 mg/kg and cZnO 10 mg/kg were equal. When injected intraperitoneally, naloxone increased anxiety but did not inhibit the anxiolytic effect of nZnO and cZnO. The anxiolytic effects of morphine potentiated the anxiolytic effects of ZnO, particularly nZno. When introduced via intra CA1 injection naloxone alone had no effect on anxiety behaviors and did not inhibit the anxiolytic effect of nZnO. Conclusion: It seems that the opioidergic system activity involved in the anxiolytic effect of nano and conventional ZnO may operate through shared and unshared pathways.