When Drosophila (fruit fly) larvae detect the presence of predators or noxious stimuli in the wild, they elicit a sequential body bending and corkscrew-like rolling response in order to escape and survive.

UWindsor researchers in the laboratory of biomedical sciences professor Jeffrey Dason employ a thermal nociception assay to trigger this response. The investigative procedure involves holding a hot probe on the cuticle of a larva, causing the larva to roll and curl.

Employing the thermal nociception assay, a study by Dr. Dason has been able to identify a role for the Drosophila foraging gene in triggering this escape response.

“We’ve found larvae with higher levels of foraging display increased sensitivity to nociception, whereas larvae with less foraging have decreased sensitivity to nociception,” says Dason. “Nociception is a process in which sensory neurons relay the perception of pain and allow an organism to avoid potential tissue damage and death.”

The process of nociception in the fruit fly is remarkably similar to how it works in mammals, including humans. This Drosophila model of nociception has been used to identify genes and mechanisms that were later shown to have similar functions in humans.

Vanessa Montemurri, recipient of an undergraduate student research award from the Natural Sciences and Engineering Research Council (NSERC), assisted Dason by utilizing light to stimulate a subset of neurons associated with the foraging gene and identified a neural circuit for this nociceptive response.

“Optogenetics is a way of activating neurons with light,” says Montemurri. “You can transgenically express light-activated ion channels in neurons and then depolarize these neurons by flashing light to activate these channels. This allows you to make a neuron fire in response to light. It’s a way for us to be able to turn on and turn off a neural circuit.”

When the nociceptive neural circuit was activated during different times in the Drosophila larvae’s development, their rolling response was affected. This suggests that prior experiences in development can affect nociceptive sensitivity.

“Our next step is to identify additional genes involved in nociception.” says Dason. “These findings will expand our knowledge of the underlying mechanisms of nociception and identify new molecules that can potentially be targeted in treating pain.”

Their collaborative publication, “Drosophila melanogaster foraging regulates a nociceptive-like escape behavior through a developmentally plastic sensory circuit,” can be read online at the Proceedings of the National Academy of Sciences of the United States of America.

—Darko Milenkovic