NMDA receptors mediate suprachiasmatic nucleus (SCN) neuronal response to endothelin-3 (ET-3). (A) Violin plots of spontaneous action potential frequencies of neurons from SCN slices treated with vehicle (water), NMDA blocker (3-(2-carboxyp-iperazin-4-yl)propyl-1-phosphonic acid [CPP], 10 µm), ET-3 (10 n m), or CPP + ET-3. ET-3 significantly increased SCN firing rate, and this was blocked with CPP (CPP × ET-3 interaction, H₍₁₎ = 30.018, P < .001). Solid and dotted lines indicate median and quartiles, respectively. n = 192 (veh), 195 (CPP), 183 (ET-3), and 187 (CPP + ET-3) cells; 4 mice per group. ^****P < .001 compared to all other groups. (B) Representative loose-patch traces (5 s) from each group. Scale bars: 2 s, 50pA. (C) Percentage of silent (empty bars) versus spiking (filled bars) for cells differed between treatment groups (3-way interaction, χ²₍₁₎ = 18.157, P < .001), with ET-3 slices having significantly more spiking cells than all other groups (P < .05).