Modulation of locomotion and motor neuron response by the cohesive effect of acute and chronic feeding states and acute d-amphetamine treatment in zebrafish larvae.

Amphetamine (AMPH) increases locomotor activities in animals, and the locomotor response to AMPH is further modulated by caloric deficits such as food deprivation and restriction. The increment in locomotor activity regulated by AMPH-caloric deficit concomitance can be further modulated by varying feeding schedules (e.g. acute and chronic food deprivation and acute feeding after chronic food deprivation). However, the effects of different feeding schedules on AMPH-induced locomotor activity are yet to be explicated. Here, we have explored the stimulatory responses of acutely administered d-amphetamine in locomotion under systematically varying feeding states (fed/sated and food deprivation) and schedules (chronic and acute) in zebrafish larvae. We used wild-type and transgenic[Tg(mnx1:GCaMP5)] zebrafish larvae and measured swimming activity and spinal motor neuron activity in real-time in time-elapsed and cumulative manner pre- and post-AMPH treatment. Our results showed that locomotion and motor neuron activity increased in both chronic and acute food deprivation post-AMPH treatment cumulatively. A steady increase in locomotion was observed in acute food-deprivation compared to an immediate abrupt increase in chronic food-deprivation state. The ad libitum-fed larvae exhibited a moderate increase both in locomotion and motor neuron activity. Conversely to all other caloric states, food-sated (acute feeding after chronic food deprivation) larvae moved moderately less and exhibited a mild decrease in motor neuron activity after AMPH treatment. These results point to the importance of the feeding schedule in modulating amphetamine's characteristic stimulatory response on behavior and motor neurons.