ABSTRACT
Twenty-four hours after mice are exposed to a single session of forced swimming in cold water, the ability of MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist, to antagonize electrically precipitated seizures is reduced. Conceivably, this reduction in MK-801's antiseizure efficacy reflects a stress-induced alteration in NMDA receptor-mediated neurotransmission due to changes in gene expression 24 h after a single stress. Recently, epigenetic interventional strategies impacting expression of genes whose regulation is controlled by the acetylation status of histone proteins in the nucleosome, an octomeric complex of histone proteins and promoter regions of double-stranded DNA, have been tested in preclinical models of various neuropsychiatric disorders, including Huntington disease and major depression. These strategies have been studied extensively in cancer biology. In the current investigation, the severity of the stress-induced reduction of MK-801's ability to raise the threshold voltage for the elicitation of tonic hindlimb extension was reduced when sodium butyrate (1.5 g/kg, ip) was administered around the time of stress. Prior research showed that this dose of sodium butyrate reliably increased the acetylation status of H3 and H4 histone proteins in the hippocampus and cerebral cortex of mice. Thus, the attenuation of the stress-induced reduction of MK-801's antiseizure efficacy may be due to the increased acetylation of histone proteins in the nucleosomal core and promotion of gene expression. These data encourage development of epigenetic strategies to prevent some of the deleterious consequences of stress.
