Hypoxia-Induced Motor and Sensory-Cognitive Deficits in Drosophila melanogaster: Insights from Chemotaxis, Phototaxis, and Locomotion Assays
Hypoxia-Induced Motor and Sensory-Cognitive Deficits in Drosophila melanogaster: Insights from Chemotaxis, Phototaxis, and Locomotion Assays
Masoud Fereidoni,1,*Seyed HesamOdin Dabooeian Tabari,2
1. Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad 2. Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad
Introduction: Ischemic stroke is a leading cause of motor and cognitive impairments, highlighting the need for effective model organisms to understand its underlying mechanisms. Drosophila melanogaster, with its well-characterized nervous system, rapid generational turnover, and high genetic similarity to humans, serves as a valuable model for studying ischemia-induced neurological deficits. Approximately 75% of human disease-associated genes and the entire hypoxia-induced cascade are conserved between flies and humans, making Drosophila particularly useful for investigating hypoxia’s effects on brain function. This study aims to assess motor and sensory-cognitive impairments in Drosophila following hypoxic exposure, using behavioral assays such as chemotaxis in response to acetic acid, phototaxis, and locomotion . These assays allow for a multi-dimensional evaluation of sensory processing, decision-making, and motor coordination, providing insights into neurological deficits induced by stroke.
Methods: Fly Preparation
Wild-type Drosophila melanogaster (0-5 days old) were divided into control and experimental groups. Hypoxia was induced at 2.5, 4, and 6 hours using a device that reduces oxygen levels while maintaining environmental conditions. After recovery, behavior was assessed through various assays.
Chemotaxis Assay
A 20 cm vial divided into four areas was used to test chemotaxis. A cotton ball saturated with 5% acetic acid was placed at the top. Flies' positions were recorded, focusing on their movement away from the acetic acid toward the farthest area.
Locomotion Assay
General motor activity was assessed in an arena where flies could walk freely without flying. Movements were tracked to evaluate total distance traveled, speed, and rest periods. Hypoxia-treated flies were compared with controls to assess motor deficits.
Phototaxis Assay
Two setups were used:
1. Dark Box Setup: Flies were placed in a dark box connected to a 20 cm vial divided into four parts. After 30 minutes of darkness, a light source was turned on, and flies’ positions were recorded to measure their light response.
2. Two-Vial Setup: Two connected vials were used, one covered in aluminum foil to create darkness. A light source illuminated the other vial, and flies’ positions in the light or dark vial were recorded.
Results: Flies exposed to hypoxia showed impairments in all assays.
In the chemotaxis assay, control flies consistently moved to the farthest section of the vial, avoiding the acetic acid. In contrast, some hypoxia-treated flies responded correctly, but over half wandered, suggesting sensory or cognitive disruptions.
In the locomotion assay, hypoxia-treated flies traveled shorter distances and rested more frequently, indicating increased fatigue and impaired motor function.
For phototaxis, in the dark box setup, more than half of the control group stayed near the light, while the ischemia group showed a reduced tendency to remain there. Many ischemia-treated flies initially moved toward the light but dispersed randomly after a few minutes. In the two-vial setup, control flies mostly chose the illuminated vial, whereas fewer hypoxia-treated flies did so, further highlighting sensory deficits.
Conclusion: These results indicate that flies exposed to hypoxia under well-controlled conditions show clear deficits across behavioral assays. Impairments in motor function were evident in the locomotion assay, while disruptions in sensory-cognitive processes, such as decision-making and memory, were observed in the chemotaxis and phototaxis assays. This suggests that ischemic injury affects both movement and higher-order neural functions, offering insights into the broader effects of brain ischemia.