The effect of chronic administration of zinc oxide and nanolZinc oxidel on anxiety behaviors of rats in the presence and absence of aerobic exercise activity

Recently it has been shown that acute administration of nano zinc oxide has stronger anxiolytic effect than conventional zinc oxide. Exercise can also reduce the level of anxiety in athletes. This study is done to clarify the effect of chronic administration of nano and conventional ZnO alone and in the presence of aerobic exercise on anxiety behaviors. Male Wistar rats (185 ± 10 gr) divided into these groups of control، exercise (6 weeks)، recipient of nano zinc oxide and zinc oxide (1mg / kg I. P) daily for 6 weeks alone and with exercise activity. Groups with exercise activity started their practice 30 minutes after injection which has based on training protocol. After 6 weeks، the anxiety indexes (time percentage that they present in open arm (% OAT) and percentage of open arm entries (%OAE)) and locomotor activity were assessed by the elevated plus maze. Exercise activity، ZnO and nano ZnO show reduced anxiolytic effect by increasing %OAT (P<0. 05، P<0. 01 and P<0. 001 respectively) and %OAE (respectively P<0. 05، P<0. 05 and P<0. 01) without any change in locomotor activity. Anxiolytic effect of nano ZnO with exercise activity was maintained in comparison with exercise activity alone %OAT (P<0. 05) while this effect was not observed for conventional ZnO. It seems، that chronic administration of nano ZnO has more significant anxiolytic effect than its conventional form and this effect is maintained in presence of exercise. The different effect of nano ZnO in compared to ZnO beside of exercise can be due to properties related to size of nanoparticles that increase their efficacy in compared to conventional form.