Effects of anxiolytic doses of ZnO nanoparticle on ECG parameters in restraint and non-restraint ovariectomized female rats

Based on our previous studies about nano-ZnO effects on physiological behaviors, in this study we have investigated the effects of anxiolytic doses of nano-ZnO on electrocardiogram (ECG) sings changes in the restraint and non-restraint ovariectomized (OVX) female rats. Animals (160-180 g) were divided into: control (non-OVX + saline) and OVX groups that received: saline, nano-ZnO 1, 2.5 and 5 mg/kg, stress of 90 or 180 min + saline and stress of 180 min+ nano-ZnO 2.5 mg/kg. Anxiety-like behaviors were measured by the elevated plus maze (EPM) and hole board apparatus thirty min after intraperitoneally injections or stress induction. ECG parameters and serum zinc level were measured in all groups. Ovariectomy induced anxiety and restraint stress in OVX rats increased it in the hole board test. Nano-ZnO 2.5 and 5 mg/kg improved anxiety-like behaviors in the EPM test. Nano-ZnO 2.5 mg/kg improved anxiety induced by the restraint stress in the hole board test. Nano-ZnO increased zinc level in a dose-dependent manner in the non-restraint OVX groups. Nano-ZnO 1 mg/kg decreased QRS amplitude and all doses decreased QT interval to the level of non-OVX group. Nano-ZnO 5 mg/kg decreased QTc to the level of non-OVX group. Stress of 90 min increased QT interval while stress of 180 min decreased it. Nano-ZnO after stress induction could alleviate heart rate, R-R- interval and QRS interval to the level of non-OVX group. It seems that nano-ZnO rather than could improve anxiety, alleviated ECG parameters in the restraint and non-restraint OVX rats.