The objective of this project is to understand how changes in the signaling of Akt, a kinase activated by insulin, among other mechanisms, regulates responses to amphetamine (AMPH). Dopamine (DA) transporters (DATs), which largely control DA clearance, are targets for psychostimulants such as AMPH, which acts to induce reverse transport of DA, increase synaptic DA levels and enhance dopaminergic transmission, with profound effects on behavior. Exciting new experiments in vitro suggest that insulin, through Akt/protein kinase B signaling, regulates DAT function by fine-tuning DAT plasma membrane expression. In concert with previous evidence, this project aims to explore, in vivo, with biochemical, behavioral, and physiological measurements, the role of Akt in DAT function and trafficking. In addition, we will determine how Akt affects the ability of AMPH to cause DA efflux. Interestingly, our preliminary data shows that diet-induced obesity (DIO) in rats leads to deficits in striatal Akt activity and DAT cell surface expression. Thus, our DIO model offers the unique opportunity to explore the effect of a calorically dense diet on Akt, DAT function, and AMPH actions.
We aim to create a platform of discoveries possibly uncovering commonality of mechanisms between food intake and DA related diseases such as psychostimulant abuse. The proposed studies address the following Specific Aims: 1. To demonstrate that pharmacological or viral regulation of Akt signaling causes DAT trafficking and, as a consequence, affects AMPH-mediated DA efflux and locomotor response to AMPH. 2. To demonstrate, in vivo, that unrestricted access to high fat (HF) diet reduces striatal Akt phosphorylation and AMPH-induced DA efflux via impairments in DAT trafficking, and to confirm the significance of Akt in these phenomena through viral rescue of this pathway in midbrain DA neurons.
Obesity and Type II diabetes are associated with insulin resistance and higher prevalences of many dopamine- related diseases, such as attention-deficit disorder, schizophrenia, and Parkinson's disease. Intriguingly, the protein kinase Akt, which is associated with insulin resistance and obesity, has recently been shown to modulate addictive responses to opiates, which suggests that Akt signaling may be crucial for normal dopamine-dependent functions such as reward. Our proposal uses biochemical, physiological, and behavioral tools to explore molecular mechanisms that explain how Akt signaling can modulate neurotransmitter systems associated with the control of reward and motivated behaviors.
