Effect of in vivo exposure to ambient fine particles (PM2.5) on the density of dopamine D2-like receptors and dopamine-induced [35S]-GTPγS binding in rat prefrontal cortex and striatum membranes

Abstract

Male Sprague-Dawley rats (8-9 weeks-old) were exposed for three days (acute exposure) or eight weeks (subchronic exposure) to purified air or concentrated ambient fine particles, PM_2.5 (≤2.5 μm; 15 to 18-fold of ambient air; 370-445 μg/m³). In membranes from rat prefrontal cortex (PFC) or striatum, the density and function of dopamine D₂-like receptors (D₂Rs) were assessed by [³H]-spiperone binding and dopamine-stimulated [³⁵S]-GTPγS binding, respectively. Glial activation was evaluated by immunoperoxidase labeling of the glial fibrillary acidic protein (GFAP). In the PFC, no significant changes in D₂R density or signaling were observed after the acute and subchronic exposure to PM_2.5. In the striatum, acute exposure to PM_2.5 decreased D₂R density, with no effect on signaling efficacy, whereas subchronic exposure did not affect D₂R density but reduced signaling efficacy. Both acute and subchronic exposure to PM_2.5 induced reactive gliosis in the striatum but not in the PFC. These results indicate that exposure to PM_2.5 induces astrocyte activation and alters striatal dopaminergic transmission.

Keywords: D(2) receptor; Dopamine; Fine particles; PM(2.5); Prefrontal cortex; Striatum.