The Influence of Multiwalled Carbon Nanotubes on the Behavior of Mammals after Single Intrapharyngeal or Intravenous Exposure

The toxic effects of multiwalled carbon nanotubes (MWCNTs) in mammals are important to assess due to MWCNTs are a widespread environmental pollutant. MWCNTs were tested for the effect on the behavioral functions of laboratory mice in the open field, rotarod, and elevated plus maze tests. Two possible routes of MWCNT entry into the body were examined: intrapharyngeal aspiration and intravenous administration, in order to model the most common ways of MWCNT entry, through the lungs and by assimilation from the blood through blood–tissue barriers. The potential toxin was administered once intrapharyngeally at 20 μg per mouse or intravenously at 0.2 μg per mouse. Acute and delayed effects were evaluated 24 h and 30 days after administration. Latent emotional tension and weaker exploratory reactions were observed 24 h after intrapharyngeal MWCNT aspiration. Signs of stress were still detectable 30 days after exposure. In contrast, an increase in locomotor and exploratory activities was observed 24 h after intravenous MWCNT administration. The result was explained by an inhibitory MWCNT effect on the lower respiratory tract and a potential lack of MWCNT accumulation in organs because MWCNTs were relatively large in size and could not penetrate through blood–tissue barriers.