A group of researchers at the University of Sao Paulo’s Ribeirao Preto Medical School (FMRP-USP), Brazil, has found that cannabidiol (CBD), the non-psychoactive compound in cannabis, can reduce isolation-induced aggressiveness in lab mice.
For the study led by Francisco Silveira Guimaraes, the researchers used what they call a resident-intruder test, which induces aggressiveness in mice subject to isolation for several days.
Researchers injected 4 groups of mice with different doses of CBD, while the 5th group acted as a ‘control’ and did not receive any dose of the cannabinoid, displaying “classic resident-intruder behavior”.
In the control group, the resident mice attacked the intruders 2 minutes after they were confronted on average. Around 20-25 attacks were recorded while the animals were in the same cage.
In the first group, wherein the resident mice were administered a CBD dose equivalent to 5 mg/kg, attacks began approx 4 minutes after intruders entered the cage — double the time taken than control mice to begin attacking intruders — and the number of attacks was reduced by half.
The second group was bestowed with a dose of 15 mg/kg and behaved the least aggressive of the lot. Attacks began 11 minutes after the intruder’s arrival on average; the number of attacks averaged only approx 5 per cage.
The 3rd and the 4th group received heavier doses- 30mg/kg and 60 mg/kg respectively and showed contrasting behavior. Attacks began sooner, and their number was also slightly higher.
“Our study shows that moderate doses of cannabidiol (CBD) can inhibit aggressiveness by facilitating the activation of two receptors: 5-HT1A, responsible for the effects of the neurotransmitter serotonin (the happiness hormone) and CB1, responsible for the effects of endocannabinoids,” said Guimaraes. “We know that CBD has anti-depressant, anti-psychotic and anxiolytic properties, which are a must-have in any aggression reducing drug.
The study didn’t conclude right there. In the second batch of experiments, the researchers repeated the resident-intruder model, however, this time 5-HT1A receptor antagonist WAY100635 was administered prior to injecting CBD. This was done to see whether the anti-aggressive effect could be canceled out using WAY100635.
The researchers found that all mice given WAY100635 before CBD, irrespective of the dose, attacked intruders almost as many times as the controls.
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