FIGURE 5.

NPY inhibits nitric oxide production via Y₁ receptor activation. Microglia cells were treated with a selective Y₁ receptor agonist [Leu³¹,Pro³⁴]NPY (1 μm) and a selective Y₁ receptor antagonist BIBP3226 (1 μm) to determine the effect of Y₁R activation on LPS-induced nitrite production. A, cells challenged with LPS and treated with [Leu³¹,Pro³⁴]NPY display nitrite production similar to control levels. Accordingly, when cells were pretreated with BIBP3226, no NPY inhibitory effect was observed. B, the involvement of other receptors was excluded with the use of selective antagonists for Y₂ receptor (BIIE0246; 1 μm) and for Y₅ receptor (L152-804, 1 μm). When Y₂R and Y₅R were blocked, NPY inhibited NO production stimulated by LPS. Data are expressed as mean ± S.E. (error bars) (n = 3 for A, and n = 4 for B) and as a percentage of control (***, p < 0.001, using Bonferroni's multiple comparison test).