You say your mom doesn’t give you enough to feel guilty about? Science is ready to step in and help. A new study found that insects can feel chronic pain – the kind they might get when the swatter only maims them and they’re able to crawl away before you can roll up a magazine and try again. Remember all those flies and spiders you’ve probably done this to? How about the bugs you collected in jars and forgot about? Feeling guilty yet?
“So we knew that insects could sense ‘pain’, but what we didn’t know is that an injury could lead to long lasting hypersensitivity to normally non-painful stimuli in a similar way to human patients’ experiences.”
Associate Professor Greg Neely at the University of Sydney led the study which was published recently in the journal Science Advances. The press release describes how his research team used fruit flies (Drosophila) – you know, the ones you bat away from grapes or your face – to determine if they (and most likely all insects) can suffer from neuropathic pain … the kind humans get from sciatica, back stress, cancer, diabetes or accidental injury. This type of chronic pain has been difficult to treat with drugs (see “opioid epidemic”) or physical therapy. Neely thought that by intentionally injuring fruit flies by damaging a nerve in a leg (low guilt level) and watching how they cope, he might learn something that could help humans.
“After the animal is hurt once badly, they are hypersensitive and try to protect themselves for the rest of their lives. That’s kind of cool and intuitive.”
If you’ve wondered how a certain annoying fly seems to excel at swatter avoidance, it could be because it remembers a previous painful-but-not-fatal encounter. After Neely injured the flies and then allowed them to heal (it’s a very complex and humane test – check out the “Fly injury model” section of the study), he saw that they seemed to now have a “hypervigilant” avoidance system which he traced to the fly’s ventral nerve cord (its spinal cord). The ventral nerve cord normally regulates or “brakes” pain, but after an injury it removes the brakes permanently, constantly and painfully reminding the flies of how bad it was the last time. In fruit flies looking to survive to buzz another grape, this is a good thing. In humans … not so much.
“Animals need to lose the ‘pain’ brakes to survive in dangerous situations but when humans lose those brakes it makes our lives miserable. We need to get the brakes back to live a comfortable and non-painful existence.”
Neely calls this “brake” in humans “central disinhibition” and, like in the fruit flies and other insects, it was once crucial to our survival as well.
“Our studies are in line with previous work that suggests that neuropathic responses may have originally been beneficial, and the heightened state of vigilance injured invertebrates exhibit may have provided an evolutionary protective advantage after serious injury. Thus, while acute nociception first evolved more than ~500 million years ago, neuropathic pain also appears to be an ancient and conserved response.”
Now that we know the ancient cause of our chronic pain, we need a modern solution that’s safe, non-addictive and covered by insurance. The answer?
“We are focused on making new stem cell therapies or drugs that target the underlying cause and stop pain for good.”
Stem cells are fast becoming the solution to many problems … except guilt. If this story has left you in a state of chronic remorse over the thousands, if not millions, of insects you’ve half-swatted or watched buzz away erratically after glancing off your car windshield, put out a bowl of grapes and leave them alone for a few days.
Then go call your mom.