Fluorescence images (40×) showing IL-1β immunoreactivity in the hypothalamus of saline- and MDMA (12.5 mg/kg, i.p.)-treated rats (1 h and 3 h after injection). Double immunofluorescence with IL-1β (red staining) and NeuN or OX-42 (both green staining, upper and lower panels respectively) revealed that IL-1β is constitutively expressed in neurons and that following MDMA the immunoreactivity for IL-1β overlaps with OX-42 immunostaining. Scale bar = 50 μm. Inset shows a stained microglial cell (63×). Same brain sections were studied as indicated in Figure 3a.