Altered Neurogranin Phosphorylation and Protein Levels Are Associated with Anxiety- and Depression-Like Behaviors in Rats Following Forced Swim Stress

Abstract

Here we tested the hypothesis that stress-induced alterations in Neurogranin (Ng) synthesis and/ or utilization might underlie stress-related depression and anxiety. Rats were randomly divided into five conditions: chronic swim stress (CS), acute swim stress (AS), and three control groups. The CS group was exposed to daily swim stress (5 min/day) for 14 consecutive days, the AS group received a single swim stress, and control groups were maintained in a stress-free condition. Both before and after swim stress, rats were tested for body weight gain, open-field locomotor activity, and saccharine preference. Ng and phospho-Ng (P-Ng) levels in the hippocampus and prefrontal cortex were determined by Western blot analysis. Compared to controls, CS animals displayed significantly decreased body weight gain, ambulation, and saccharine intake, and increased grooming behavior. CS animals had decreased Ng levels in the hippocampus and prefrontal cortex. In CS animals, Ng levels were positively correlated with saccharine intake and ambulation, and inversely correlated with grooming behavior. Compared to controls, AS increased immobility behavior and P-Ng and Ng levels in the hippocampus and prefrontal cortex. In AS animals, immobility behavior was positively correlated with the P-Ng in the prefrontal cortex. Thus, CS and AS produced opposing effects on Ng and P-Ng levels in the hippocampus and prefrontal cortex. Low Ng levels in the hippocampus were associated with anhedonic behavior in CS animals, whereas high P-Ng levels in the prefrontal cortex were associated with anxiety-like behavior in AS animals. Thus, Ng dysfunction might contribute to the neural mechanisms underlying stress-induced depression and anxiety.