Effects of AMPH-Food Deprivation Interaction on Behavior and its Neural Substrates in Zebrafish Larvae

Drug abuse is a global concern, claiming nearly half a million lives around the world and a hundred thousand lives in the United States every year. This neuropsychiatric disorder begins to spread its roots from adolescence age, causing approximately 60% of teenagers to abuse drugs, especially stimulants with high abuse potential (e.g., amphetamine (AMPH)). Although acute use of the stimulants induces their reinforcing effects, such as euphoria, improved mood, and memory induced by drugs, tempt consumers to chronically abuse them, the increase in their intake is often caused by external factors, e.g., failure and pain. However, some of these risk factors go unnoticed; one example is food deprivation and restriction. This study explores the effects of food deprivation on amphetamine’s stimulatory response on behavior and the brain. We used wildtype (ABWT) strain of zebrafish to observe the changes in behavior (swimming behavior) and three different transgenic strains [Tg(mnx1:GCaMP5)- for motor neuron activity; Tg(th2:GCaMP7s)- for dopamine activity; Tg(agrp1:ChR2-kaede)- for AgRP neuron activation] for neuron activity recording and activation. In the first part of the study, we measured the swimming, cardiac, and motor neuron activity pre-and post-AMPH (0.7uM) treatment in hungry and fed zebrafish larvae and observed an increase in all the activity responses after AMPH administration in food-deprived states. In the second part, as an extension, we added food-sated and acute food-deprivation states and measured swimming distance and latency in motor neuron activity peaks. We found an abrupt increase in locomotion in chronic hunger and a slow but progressive increase in activity in acute hunger post-AMPH treatment. Swimming activity in food-sated larvae moderately decreased over time after administering the drug. A similar activity trend in motor neuron calcium peaks was observed. In the third part, we observed the dose-dependent (0.7uM and 1.5uM) change in dopamine (DA) neuron firing in food-deprived and fed states in different DA regions of the hypothalamus altered inter-region activity correlation. The results showed increased DA neuron activity in all three regions of food-deprived states without and with AMPH doses. In the last part, we created a novel transgenic zebrafish line and optogenetically activated AgRP1 neurons in the larval hypothalamus and quantified the increase in food intake behavior post-neuron activation.