The use of nanoparticles (NPs) has increased in recent years and consequently they are being released into the environment. The final destination of most NPs is the aquatic environment due to washing up by rain waters. Fish (n = 120) were exposed to different concentrations (0, 1, 5, and 25 mg/L) of aluminum-oxide (Al2O3), copper-oxide (CuO), and titanium-dioxide (TiO2) NPs for 14 days and 14 days of depuration period (no NP in water). Following NP exposures, activities of Na,K-ATPase, Mg-ATPase, Ca-ATPase, and acetyicholinesterase (AChE) in the brain and muscle were measured. AChE activity in the brain and muscle decreased significantly (P < 0.05) following exposure to CuO NPs and TiO(2)NPs, although Al(2)O(3 )NPsdid not cause any significant (P > 0.05) alteration. Similarly, Ca-ATPase activity in the muscle was decreased significantly by Al(2)O(3)NPs and CuO NPs, but not by TiO2 NPs. Total ATPase and Mg-ATPase activities did not alter significantly in the brain, though Na,K-ATPase activity decreased after exposure to CuO NPs. Half (n= 60) of the NP-exposed fish were transferred to NP-free waters for depuration experiments for 14 days. Transmission electron microscope images demonstrated NP aggregates in the tissues, although some NPs were retained in the tissues after the depuration. This study showed that NPs are able to alter nervous system biomarkers, copper NP being the most effective one.