Anxiolytic-like actions of centrally-administered neuropeptide Y, but not galanin, in C57BL/6J mice

Neuropeptide Y (NPY) and galanin (GAL) are densely localized in brain regions subserving stress, fear and anxiety. While previous research supports a role for both neuropeptides in the mediation of rodent emotional behaviors, there is currently a lack of information on the effects of central administration of NPY and GAL on fear- and anxiety-related behaviors in mice. In the present study, the effects of intracerebroventricularly administered NPY and GAL were assessed in C57BL/6J mice on a battery of tests for fear- and anxiety-related behavior. NPY (0.5, 1.0 nmol) produced clear anxiolytic-like effects in the elevated plus-maze and light↔dark exploration test, whereas GAL (0.5, 1.0 nmol) was without effect. NPY (0.5 nmol) also increased locomotor activity in the open field test. In the fear conditioning paradigm, NPY administered prior to training reduced freezing to context (0.5, 1.0 nmol) and auditory cue (1.0 nmol). Pre-training GAL (0.5 nmol) treatment reduced freezing to context. Taken together, results demonstrate robust effects of centrally-administered NPY, but not GAL, on anxiety-like behaviors and fear conditioning in mice. These findings provide a basis for future studies of mice with targeted gene mutations, directed at delineating the anatomical regions and receptor subtypes mediating the effects of NPY and GAL on emotion.