# Does Nanosilver Have a Pronounced Toxic Effect on Humans?
## 2 Results of Investigations Performed by Other Researchers
### Effect of AgNPs on the Brain and Behavior
For other  
Figure 1: Possible mechanisms of AgNPs for crossing the blood–brain barrier [39; 40; 41]. NPs and Ag+, the induction of peripheral inflammation, which was reflected by alterations in the level of serum inflammatory mediators, was observed [47]. [PERSON] et al. [48] showed a significant reduction in GAP-43 mRNA and protein expression in the hippocampus of offspring exposed to uncoated AgNPs, suggesting cognitive impairments in rats. However, in some studies on adult animals, after subchronic contact with AgNPs, no behavioral disturbances were noticed. In the study by [PERSON] et al. [49], no significant differences between experimental and control mice in the formation of spatial and working memory were found, and secondary neurogenesis in the hippocampus was not impaired. In the research by [PERSON] et al. [12], pathological changes in the structure of myelin sheaths and a decrease in the level of three myelin-specific proteins were detected in the brain of experimental rats treated with AgNPs or Ag+. However, neither motion nor exploratory behavior or memory was impaired in animals treated with silver nanoparticles present in the two forms. After an intranasal introduction of AgNPs, experimental mice coped with the recognition of a new object in the same way as the control ones; however, their spatial memory was presumably impaired, while the ability for spatial learning itself did not decrease [50]. After AgNPs were injected into lactating mice, their grown offspring, which contacted with AgNPs through milk, did not differ from control animals in terms of their emotional state, social interactions, and locomotion [51]. A summary of the experiments on the influence of AgNPs on different model organisms is given in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Animals**} & \multirow{2}{*}{**Study Goal**} & \multirow{2}{*}{**Coating**} & \multicolumn{2}{c}{**Dose of AgNPs**} & \multicolumn{1}{c}{**Amount of**} & \multirow{2}{*}{**Effect**} & \multirow{2}{*}{**Reference**} \\  & & & **and Method of** & & & & \\  & & & **Admission** & & & & \\ \hline \multirow{6}{*}{Adult rats (age 12 to 14 weeks)} & Influence of & & & & The permeability of & \\  & long-term sleep & & & & the blood–brain & \\  & deprivation on & & & intraperitoneal & & barrier increased in \\  & the blood–brain & & & injection once per & & direct proportion to \\  & barrier function & & & day for 7 days & & the dose of AgNPs \\  & and & & & & & received by \\  & brain pathology & & & & & animals. \\  & & & & & & Increased body \\  & & & & & weight and body & \\  & & & & & temperature of & \\  & & & & & below the & AgNP-treated \\  & Effects of the & & & detection limit & animals. Both \\  & oral & & & 0.2 mg/kg per & of the & nano-Ag and Ag+ \\  & administration & & & day for 14 days; & inductively & induce \\  & of AgNPs or & Citrate & & through a & coupled plasma & pathological \\  & silver ions on & & gastric tube & & mass & changes in the \\  & behavior and & & & spectrometry in & structure of myelin \\  & cerebral myelin & & & brain & sheaths and a \\  & & & & homogenates & decrease in the \\  & & & & & level of three \\  & & & & & myelin-specific \\  & Assessment of & & & & proteins. \\  & the potential & & & & The hyperactivity \\  & toxicity of envi- & & & & of larvae in \\  & (embryos, & & & 3 ppm (mg/L); & \\  & larvae) & relevant & & from 4 to 120 h & \\  & concentrations & & post fertilization & & illumination \\  & of AgNPs & & & & changes faded after \\  & & & & & 5 days of exposure. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the experiments on the influence of AgNPs on different model organisms. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline