Aims: 

The pathophysiological effects of environmental pollutants are determined by chemical and physical characteristics. Nanoparticles, in the submicron range, are a major part of air pollutants, and their effects can be distinct from those of larger particles. In this work, manganese was given to rats in nanoparticle and dissolved form, and the effects on open field behaviour and cortical electric activity were observed and compared.

Methods: 

Male Wistar rats received intranasal instillation of dissolved MnCl₂ or nanosuspension MnO₂ (both 40 ml, equal to 2.53 mg Mn per rat) once, or for 3 and 6 weeks every workday. Five days after single administration, or at the end of the subacute treatment period, the rats had a 10 min session in an open field box, were then anesthetized with urethane, the left hemisphere was exposed, and spontaneous and stimulus-evoked activity was recorded from the primary somatosensory, visual and auditory area.

Results: 

In the open field, the rats treated once had reduced horizontal and vertical motility, while local motility and immobility was increased, and solute Mn had stronger effect. After 3-6 weeks, the effect of nanoparticle Mn was increased and the behavioural changes were more expressed. For all treated rats, the increase of the somatosensory evoked potential with increasing stimulation frequency was less than in the controls. The latency of the visual evoked response was lengthened more by nanoparticle than by solute Mn.

Conclusion: 

The effects of Mn in nanoparticle vs. dissolved form were qualitatively similar. The quantitative differences may indicate differences in absorption and kinetics.