It has long been known that cannabis use in humans can lead to ‘the munchies’. According to a new study, worms get them too – and like people, they not only eat more food after exposure, but prefer to reach for their favourite snacks while under the influence.
The research, published in Current Biology, found the active chemicals known as cannabinoids in the drug affects Caenorhabditis elegans nematodes – a type of roundworm – in a very similar way to humans, despite the fact the two species set off on very different evolutionary paths more than 500million years ago.
In addition, the team found that when replacing the worms’ cannabinoid receptors with human receptors using genetic engineering, the worms responded in the same way. The results could have practical implications in the development of drugs that target the same receptors.
‘Cannabinoids make nematodes hungrier for their favoured foods and less hungry for their non-favoured foods,’ said Shawn Lockery, from the University of Oregon in Eugene. ‘Thus, the effects of cannabinoids in nematodes parallels the effects of marijuana on human appetites.’
Cannabinoid receptors, found in the brain, nervous system and other parts of the body, evolved to respond to endocannabinoids, naturally occurring molecules that play an important role in eating, anxiety levels, learning and memory, reproduction and metabolism among others.
For the nematodes, a ‘favoured food’ is a particular bacteria. Two types of bacteria were placed in a T-shaped maze – one a ‘superior’ food in the left-hand side, and one ‘inferior’ in the other. The team then counted the number of worms exposed to cannabinoids in each food patch at 15-minute intervals for one hour.
‘We found that the sensitivity of one of the main food-detecting olfactory neurons in C. elegans is dramatically altered by cannabinoids,’ said Lockery. ‘On cannabinoid exposure, it becomes more sensitive to favoured food odours and less sensitive to non-favoured food odours.
‘This effect helps explain changes in the worm’s consumption of food, and it is reminiscent of how THC [tetrahydrocannabinol] makes tasty food even tastier in humans.’
On the practical applications of the study, Lockery added: ‘Cannabinoid signalling is present in the majority of tissues in our body. It therefore could be involved in the cause and treatment of a wide range of diseases.
‘The fact that the human cannabinoid receptor gene is functional in C. elegans food-choice experiments sets the stage for rapid and inexpensive screening for drugs that target a wide variety of proteins involved in cannabinoid signalling and metabolism, with profound implications for human health.’
However, the study did throw up another question – how cannabinoids affected the nematodes’ olfactory neurons, which do not have cannabinoid receptors.
Next up, the team may study the effect of psychedelics on nematodes.
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