Selective Deletion of the Leptin Receptor in Dopamine Neurons Produces Anxiogenic-like Behavior and Increases Dopaminergic Activity in Amygdala

Leptin receptors (Lepr) are expressed on midbrain dopamine neurons. However, the specific role of Lepr signaling in dopamine neurons remains to be clarified. In the present study, we generated a line of conditional knockout mice lacking functional leptin receptors selectively on dopamine neurons (Lepr(DAT-Cre)). These mice exhibit normal body weight and feeding. Behaviorally, Lepr(DAT-Cre) mice display an anxiogenic-like phenotype in the elevated plus-maze, light-dark box, social interaction and novelty-suppressed feeding tests. Depression-related behaviors in the chronic stress-induced anhedonia, forced swim and tail-suspension tests were not affected by deletion of Lepr in dopamine neurons. In vivo electrophysiological recordings of dopamine neurons in the ventral tegmental area (VTA) revealed an increase in burst firing in Lepr(DAT-Cre) mice. Moreover, blockade of D1-dependent dopamine transmission in the central amygdala by local microinjection of the D1 antagonist SCH23390 attenuated the anxiogenic phenotype of Lepr(DAT-Cre) mice. These findings suggest that leptin receptor signaling in midbrain dopamine neurons has a crucial role for the expression of anxiety and for the dopamine modulation of amygdala function.