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Strain Differences Influence N-Methyl-D-Aspartate Receptor Subunit Gene Expression in the Olfactory Bulb of an Allergic Mouse Model following Toluene Exposure

Objective: Genetic variation is a causative factor in differing sensitivities to environmental chemicals. The present study explored whether differences in mouse strains influence N-methyl-D-aspartate (NMDA) receptor expression in the olfactory bulb after low-level toluene exposure. Methods: Ten-week-old male C3H/HeN (H-2k), BALB/c (H-2d) and C57BL/10 (H-2b) mice were exposed to 0, 5, 50 or 500 ppm of toluene for 6 h per day, 5 days per week for 6 weeks. Because individuals with allergic disease are more susceptible to volatile organic compound exposure, the animals of each strain were divided into 2 main groups, a non-allergy (NAG) group and an allergy (AG) group. The AG groups were stimulated with ovalbumin before toluene exposure. The mRNA levels of NMDA receptor subunits (NR1, NR2A and NR2B) in the olfactory bulbs of the NAG and AG groups were examined using real-time RT-PCR. Results: In C3H/HeN mice, the expression levels of NR1 and NR2B mRNA decreased significantly in the AG group exposed to 500 ppm of toluene; in the NAG group, however, the NR2A mRNA level increased significantly in mice exposed to 50 ppm while the NR2A and NR2B mRNA levels decreased significantly in mice exposed to 500 ppm of toluene. No significant changes were observed in the NAG groups of BALB/c or C57BL/10 mice. However, in the BALB/c mice, the mRNA levels of NR1, NR2A and NR2B decreased significantly in the AG group exposed to 500 ppm of toluene. Conclusion: Mammalian strain differences in NMDA receptor expression after allergic stimulation can be observed in the mouse olfactory bulb after toluene exposure.