3,6′-Dithiothalidomide (56 mg/kg i.p.) treatment attenuates the aberrant expression of Arc mRNA induced by intercerebroventricular administration of LPS after a uniform level of behavioral activity. Representative flat images of neurons labeled for Arc mRNA (red) within the DG, after behavioral exploration of a novel environment for 10 min. Nuclei are counterstained in green. The upper panel illustrates the numbers of Arc positive (+ve) cells in animals infused with aCSF and treated with drug vehicle. The middle panel displays the numbers of Arc + ve cells in LPS-infused, vehicle-treated animals. The lower panel shows the numbers of Arc + ve cells in LPS-infused, drug-treated animals. The scale bar indicates 100 μm.