Lectures by Fellows/Associates

A Jayaraman, Bangalore University, Bengaluru

Reward memory recall: Role of glutamatergic neurotransmission in the dentate gyrus

Reward is a fundamental behaviour that drives growth and reproduction. A reward is linked with pleasant feelings towards food, sex, and drugs of abuse. The brain regions, ventral tegmental area (VTA), and nucleus accumbens (NAc) are involved in processing rewards and the value of choices available to an animal. Another brain region, hippocampus is crucial for associating rewards with the events that precede them and the context in which the reward was received. This reward association process is critical for memory-guided decision-making that deteriorates mental illnesses such as binge eating disorders (BED), drug addiction, and schizophrenia. The hippocampus also displays several aging-related cellular alterations leading to volume reductions, particularly in the dentate gyrus (DG) local excitatory (glutamatergic) and inhibitory (GABAnergic) circuit. Therefore, we focused on studying the role of glutamatergic neurotransmission in the DG in regulating reward memory recall. Adult male rats were subjected to tasks in the nose-poke operant conditioning apparatus 20 min/day for seven days. A sweet food pellet was dispensed when the rat only poked his nose in the active hole. A probe trial was conducted to check memory recall. Interestingly, intra-DG administration of glutaminase siRNA in the conditioned rats decreased the discrimination index by 48 hrs. The deficits in the recall were rescued by the exogenous BDNF administration. These results suggest that glutamatergic neurotransmission in the DG may induce reward memory recall via BDNF signaling.