Stress-mediated hyperactivity and anhedonia resistant to diazepam and fluoxetine in drosophila

Abstract

Distresses may induce behavioral phenotypes constituting heuristic models for psychopharmacology studies. In several species, including Drosophila, antidepressants counteract stress-induced phenotypes allowing the use of these models to test new psychoactive drugs. Here, we developed a novel and time-efficient protocol to provoke stress-induced phenotypes in Drosophila for the study of psychopharmacological agents. In the first experiment, flies (n=12/groups) were exposed to a random-sequence of different types of stresses during nearly 24 h (including social isolation, fasting, heat, and electric shock), a protocol named short-term variable stress (SVS). Second, flies were exposed to a single stressful stimulus (social isolation, fasting, heat shock or electric shock, n=12/groups). Next, flies submitted to SVS protocol were treated with vehicle, diazepam or fluoxetine (n=12/groups). At the end of the stress protocols, behavioral phenotypes were evaluated in the open field (OF) and sucrose preference tests. In comparison to the unstressed group, flies exposed to SVS exhibited hyperactivity, as well as shorter times exploring the boundaries of the OF.In contrast to fasting stress, SVS reduced sucrose preference in flies. By analyzing the effects of individual stimuli on fly behavior, fasting and electric shock appear to be the predominant influences on the SVS-induced behaviors. Although fluoxetine or diazepam reduced the initial locomotor activity of flies, no treatment prevented the sequelae of SVS. Altogether, this study provides a timeefficient model system for the study of stress-mediated hyperactivity and anhedonia-like state resistant to fluoxetine and diazepam. The applications of SVS in Drosophila to preclinical psychopharmacology require further studies.

Lane-maze for preference testing in flies

“…According to previous literature, food deprivation may induce hyperactivity, centrophilic behaviour and sucrose preference in flies. 20,21 In the present study, except for the small effect of food-deprivation for 8 h on the normalised times of grooming of females or immobility of males in the lane, no other obvious effect of food deprivation was observed.…”

“…In this study, a lane-maze test was designed and standardised to simultaneously evaluate behaviours related to general motor activity and fluid intake in several individual flies. In flies, motor activity 20, 31, 32, 33, 34 and fluid intake 21, 22, 23, 24, 25, 26 are often measured independently in separate apparatuses, except ARC. 27 Motor activities are often measured using automatic tracking in the open field tests, 20, 31, 32, 33, 34 while sucrose preference may be assessed in various analyses of fluid intake (e.g., CAFE 22,23 ; proboscis extension 24 ; ARC 27 ).…”

“…In flies, motor activity 20, 31, 32, 33, 34 and fluid intake 21, 22, 23, 24, 25, 26 are often measured independently in separate apparatuses, except ARC. 27 Motor activities are often measured using automatic tracking in the open field tests, 20, 31, 32, 33, 34 while sucrose preference may be assessed in various analyses of fluid intake (e.g., CAFE 22,23 ; proboscis extension 24 ; ARC 27 ). Using positional tracking of individual flies and microcapillaries, ARC 27 provides a high throughput platform for the simultaneous assessment of activity, immobility, and fluid intake.…”

“…Since the pioneer study reporting learned helplessness in flies, 18 several attempts to develop models and behavioural tests for stress response in Drosophila have been made. 19, 20 Flies trained to receive inescapable heat shocks failed to escape from the stressor even when the opportunity appeared, different from those trained with escapable heat shocks. 18 Another study demonstrated that exposure to vibrations for three days reduced the walking of flies in the climbing test.…”

“…An extremity of every lane had a capillary filled with 5% sucrose solution attached, simulating a single-bottle preference test for rodents. 16 Food deprivation is expected to induce hyperactivity and increased sucrose preference in the flies 20 , which may be accessed by scoring the categorical aspects of behaviour of flies in the lane or capillary zones. These approaches should allow for high throughput testing to plan well-powered studies to investigate the behavioural signs of stress in D. melanogaster .…”