Figure 3.

MDH infusion of CART 55-102 reinstates both extinguished alcoholic beer and sucrose seeking in the extinction context. A, Low-magnification photomicrograph of MDH showing dense CART terminals and prodynorphin neurons. Scale bar, 100 μm. B, Photomicrograph of a single prodynorphin neuron showing close associations of CART terminals. Scale bar, 10 μm. C, The left panel shows mean (±SEM) responses on the active and inactive nose poke during the last day of extinction and on test for rats trained to respond for 4% alcoholic beer. MDH infusions of CART 55-102 selectively increased responding on the active, but not inactive, nose poke compared with vehicle (VEH). There was no difference in responding between MDH vehicle and either MDH CART 1-27, or LH CART 55-102. The right panel shows responses for rats trained to respond for 10% sucrose. MDH infusion of CART 55-102 selectively increased responding on the active nose poke compared with vehicle. *p < 0.05 MDH CART 55-102 vs MDH VEH active nose poke. D, CART-induced reinstatement is dependent on the expression of extinction (Ext). The left panel shows responses on the active and inactive nose pokes on test after MDH infusions of either CART 55-102 or vehicle in rats that did not receive self-administration training. CART 55-102 had no effect in untrained animals. The right panel shows responses on the active and inactive nose pokes on the last day of extinction and during test. There were no differences between groups indicating that MDH infusions of CART 55–102 have no effect on ABA context-induced reinstatement. *p < 0.05 VEH Ext vs Test. + p < 0.05 CART Ext vs Test. E, CART-induced reinstatement of extinguished alcoholic beer seeking is dose-dependent. Mean (±SEM) responses on the active and inactive nose pokes during test after MDH infusions of 0, 0.025, 0.25, and 2.5 μg of CART 55-102. CART 55-102 infusions into MDH dose-dependently increased responding on the active nose poke. *p < 0.05. 3v, third ventricle; f, fornix; VMH, ventromedial hypothalamus.