The effects of an environmental neurotoxin BMAA on locomotory behavior of drosophila

L-Glutamate controls insect locomotion both at the level of the peripheral and central nervous system. _-N-methyl-amino-L-alanine (BMAA) is considered a glutamate agonist that can cause changes in locomotory behavior of Drosophila melanogaster. Overstimulation of glutamate receptors at the neuromuscular junctions should result in loss of motor ability. Overstimulation of the glutamate receptors in the central pattern generator of the central nervous system should lead to hyperactivity (increased activity levels and walking bout duration). Flies were fed high concentrations of glutamate or BMAA (concentrations: 0, 12.5, 25, 50 mM), and their locomotory behaviors were quantified for three consecutive days using two types of assays: the tap-down assay and an assay custom-designed for this study. The tap-down assay records the flies_ climbing up a vertical incline (90_) after the tap-down (climbing in response to an external stimulus). The custom-designed assay (lenticular arena assay) uses a concave floor to quantify spontaneous climbing up a gradually increasing incline (0-15_). It also allows quantification of walking speed, walking bout duration, walking bout frequency, stumble frequency and climbing ability in order to assess locomotory changes in treated flies. The flies showed a dose-dependent response to BMAA, manifesting hyperactivity at low doses and loss of motor ability at high doses. The introduction of excess glutamate caused no significant changes in locomotory behavior.