Effect of subchronic exposure to ambient fine and ultrafine particles on rat motor activity and ex vivo striatal dopaminergic transmission

Abstract

Alterations in dopaminergic transmission are associated with neurological disorders, such as depression, autism, and Parkinson's disease. Exposure of rats to ambient fine (FP) or ultrafine (UFP) particles induces oxidative and inflammatory responses in the striatum, a neuronal nucleus with dense dopaminergic innervation and critically involved in the control of motor activity. Objectives: We used an ex vivo system to evaluate the effect of in vivo inhalation exposure to FP and UFP on motor activity and dopaminergic transmission. Materials and Methods: Male adult Wistar rats were exposed to FP, UFP, or filtered air for 8 weeks (subchronic exposure; 5 h/day, 5 days/week) in a particle concentrator. Motor activity was evaluated using the open-field test. Uptake and release of [ 3 H]-dopamine were assessed in striatal synaptosomes, and dopamine D 2 receptor (D 2 R) affinity for dopamine was evaluated by the displacement of [ 3 H]-spiperone binding to striatal membranes. Results: Exposure to FP or UFP significantly reduced spontaneous motor activity (ambulatory distance: FP À25%, UFP À32%; ambulatory time: FP À24%, UFP À22%; ambulatory episodes: FP À22%, UFP À30%), decreased [ 3 H]-dopamine uptake (FP À18%, UFP À24%), and increased, although not significantly, [ 3 H]-dopamine release (113.3 ± 16.3 and 138.6 ± 17.3%). Neither FP nor UFP exposure affected D 2 R density or affinity for dopamine. Conclusions: These results indicate that exposure to ambient particulate matter reduces locomotion in rats, which could be related to altered striatal dopaminergic transmission: UFP was more potent than FP. Our results contribute to the evidence linking environmental factors to changes in brain function that could turn into neurological and psychiatric disorders. HIGHLIGHTSYoung adult rats were exposed to fine (FP) or ultrafine (UFP) particles for 40 days. Exposure to FP or UFP reduced motor activity. Exposure to FP or UFP reduced dopamine uptake by striatal synaptosomes. Neither D 2 R density or affinity for dopamine was affected by FP or UFP. UFP was more potent than FP to exert the effects reported.