Figure 3.

CCK-8S activates orexin neuron through the CCK_AR. A, B, The effects of CCK_AR or CCK_BR agonists on the orexin neurons. CCK-8S (0.01 μm, n = 6), a CCK_AR and CCK_BR nonselective agonist, induced an inward current in orexin neurons. However, CCK-4 (1 μm, n = 5) and CCK-8NS (1 μm, n = 16), CCK_BR preferential agonists, induced weak inward current even at a high concentration. CCK-4 and CCK-8NS were dissolved in DMSO and added to extracellular solution. Final DMSO concentration in the extracellular solution was 0.1%. The extracellular solution, which contained 0.1% DMSO alone was used as vehicle control and had no effect. C, D, The effect of CCK_AR selective antagonist, lorglumide, on the CCK-8S-induced inward current. Sequentially applied CCK-8S induced almost the same amplitude of inward current. Pretreatment with lorglumide (1 μm) for 2 min inhibited CCK-8S (10 nm)-induced inward current. Δ Current was normalized to CCK-8S (10 nm) before experiments. E, F, The effect of lorglumide on CCK-8S (30 nm)-induced increase in [Ca²⁺]_i. Orexin/YC2.1 mice brain slices were used for calcium imaging of orexin neurons. CCK-8S and lorglumide were applied by bath application during the period indicated by the bar. The experiment was performed in the presence of TTX (1 μm). Lorglumide (0.1 μm, n = 6; 1 μm, n = 15; 10 μm, n = 6) inhibited CCK-8S-induced increase in [Ca²⁺]_i in a concentration-dependent manner. Values are mean ± SEM. ^*p<0.05.