When some people drink too much, they turn soppy and hug you, while others become violent and reckless. Could this be explained by our previous social experiences? This study on drunken crayfish certainly suggests so.
A new study in the Journal of Experimental Biology looked into this by putting booze into the tanks of both sociable and loner crayfish. The team of neuroscientists from the University of Maryland found that alcohol affects sociable crayfish considerably faster than the loners.
During the experiment, the crayfish were noted to have three stages of drunkenness: First, they walked around with stiff and straightened legs, then they began to flip their tail, then finally they laid on their back and had difficulty returning to an upright posture. Sounds familiar, right?
This species, Procambarus clarkii, was chosen as the guinea pigs as they have proven themselves to be good models for measuring the effects of drugs, as shown by other experiments that have seen a change in their behavior after taking recreational drugs like amphetamines and cocaine.
After putting small concentrations of alcohol into tanks, the drunkenness of the crayfish was measured via their tail-flipping. The researchers surgically inserted wires near a major nerve that controls their tail and recorded the excitation of the lateral giant interneuron (which influences the tail-flipping behavior).
The more intoxicated the crayfish were, the more sensitive the neural circuit became. They also found that crayfish who had previously been held in communal tanks became impaired notably quicker than those who had previously lived in isolated tanks.
This suggests that exposure to different social environments can cause lasting changes to neurotransmitter systems, although the study authors noted this is "somewhat speculative at this point" as they don't know the neurocelluar mechanism behind it.
"Alcohol is a complicated drug," Jens Herberholz, from the University of Maryland, explained in a statement. "Our study shows that social experience can change the sensitivity to acute alcohol." He adds: "Inebriated people... could potentially have different responses to alcohol depending on their prior social experience".
Of course, crayfish are very different to humans, but Herberholz believes these drunken crayfish could hold the potential to help us develop better treatments for humans suffering from alcohol abuse at some point in the future.