Microglial cells express histamine receptors.
(A) Histamine receptor expression analysis by real-time PCR showed that microglial cells constitutively express all known histamine receptors – H1R (74 bp), H2R (65 bp), H3R (65 bp) and H4R (109 bp). (B) LPS stimulation (100 ng/ml) did not alter the expression of H4R, quantified by Western blotting. Data are expressed as percentage of control (n = 3-4). A representative blot is shown below the graph (H4R, 44 kDa; GAPDH, 37 kDa). In both experimental paradigms, primary microglia cultures from the cortex (Cx) were used as a positive control. For qPCR, whole hippocampal cDNA was used as an additional positive control (data not shown). (C) N9 microglial cells (top panel) and primary cortical microglia cultures (bottom panel) expressed H4R (in red) under control conditions and upon LPS challenge (100 ng/ml). Cells were stained for morphology marker CD11b (in green) and Hoechst 33342 (nuclei in blue). Scale bar, 10 μm.