TORONTO - They're not exactly sitting around playing a game of Texas Hold 'em, but laboratory rats have the ability to "play the odds" just like people, say researchers, who have created an experimental animal model that mimics human gambling.
Scientists at the University of British Columbia say their risk-assessing rodents could provide a means for developing and testing drugs to treat gambling addiction in people.
"Lab rats are incredibly smart," said behavioural neuroscientist Catharine Winstanley, principal investigator of a study published Wednesday in the Nature journal Neuropsychopharmacology.
"They're capable of solving quite complex paradigms, as we've shown here, the sort of thing that you may argue that `I can't believe anything other than a human could solve."'
The paper describes how lab rats reacted to setups in which the choices they made could mean earning a reward or suffering a loss.
But the animals weren't looking for a big payoff in dollars and cents -- the currency they were salivating after came in the form of sugar pellets.
The rodents were placed in specially built boxes whose walls incorporated four "response holes." Each opening was associated with a possibility of earning treats -- from one up to four, depending on the aperture chosen.
When an animal poked its snout into a hole, the movement would break an infra-red light across the opening, signalling a computer with a "probalistic" reward-punishment schedule to assign a pellet win or a "timeout" loss.
Playing against the clock, the rats had only 30 minutes to accumulate as many sugar pellets as they could.
They quickly learned that openings with the highest rewards, three or four treats, also posed the highest risk for punishment -- a greater number of and longer-lasting timeouts, in which they could not seek pellets.
"Having to sit through these very tedious timeouts was very frustrating for them and it lost them time they could be earning reward at another location," Winstanley said from Vancouver. "So they had to learn to avoid those very tempting larger reward options and instead go for smaller reward options that would over time give them maximal gain."
In other words, the rodents were able to calculate risk and opted for a number of small wins instead of taking a chance on a jackpot.
"They had to learn that over time playing conservatively and playing safe was the best strategy," she said, noting that the animals made the optimal choice 60 to 70 per cent of the time on any given day.
The researchers also tested how the rats' responses differed after being given certain drugs to reduce levels of two brain chemicals linked to gambling behaviour.
When the rodents were given an agent that lowers serotonin, a neurotransmitter that controls mood and impulses, "what we saw was a reduced ability of our animals to discriminate the best option," said Winstanley.
"They became worse gamblers, if you like."
Interestingly, drugs to boost serotonin levels -- antidepressants like Prozac and Zoloft -- are used to treat people with a gambling addiction, she noted.
Using a compound to drop dopamine levels had the opposite effect on the rats, which improved their ability to optimize rewards, the study found.
The finding jibes with an observation of people with Parkinson's disease, some of whom develop a sudden and unexpected gambling addiction after being treated with drugs to boost diminishing dopamine levels in their brains.
"There's very few effective treatments out there" for gambling addiction, said Winstanley, who believes the lab rat model could give scientists a window into the devastating condition.
"This is very much a first step," she said. "We're really happy we can see gambling-like behaviour in our rats and now we can use this task to really probe the neural and neurochemical basis for gambling disorders."
