Effects of low-level formaldehyde exposure on synaptic plasticity-related gene expression in the hippocampus of immunized mice

We examined the effects of inhalative exposure to formaldehyde (FA, 400 ppb) on N-methyl-D-aspartate (NMDA) receptor subunits (NR2A and NR2B), dopamine receptor subtypes (D1 and D2), cyclic AMP responsive element-binding protein (CREB)-1, CREB-2, FosB/ΔFosB, and transient receptor potential vanilloid receptor (TRPV1) in the hippocampus of ovalbumin-immunized mice using quantitative real-time PCR. Western blot analyses for pCREB were performed. The mRNA levels of NR2A, D1 and D2 receptors, and CREB-1 were significantly increased by FA, but NR2B, CREB-2, FosB/ΔFosB, and TRPV1 mRNA levels remained unchanged. Treatment with MK-801 normalized the mRNA levels induced by FA. There was no significant effect of FA exposure and MK-801 treatment on the protein level of pCREB. These results indicate that FA exposure selectively up-regulates hippocampal gene expression in immunologically sensitized mice. The FA effects are presumably mediated by glutamatergic neurotransmission through NMDA receptors.