Subchronic treatment with imipramine ameliorates the decreased number in neuropeptide Y-positive cells in the hippocampus of learned helplessness rats

Learned helplessness, but not immobilization stress, decreased the numbers of neuropeptide Y (NPY)-positive cells (interneuron), but not calcitonin gene-related peptide (CGRP)-positive cells (mossy cell), in the hilus of the hippocampus. Subchronic treatment of learned helplessness rats, but not naive rats, with imipramine ameliorated the decrease in the number of NPY-positive cells. Therefore, NPY-positive cells in the hippocampus may contribute to depression.