For seven years, scientists studied their brains in a research project deemed so valuable it won a national award.

In their off-hours, the two young females played with toys, watched TV, ate fruit and hung out together in their home on the University of Toronto campus.

That home was a cage for the two monkeys, “cynomolgus macaques” bred in Texas for research.

And when they were put to death earlier this month so scientists could analyze their brains, it marked the end of primate research at Canada’s largest university.

“They were our very last ‘non-human’ primates and we have no intention of using any more. Technology now lets us get the same information from smaller animals,” said Peter Lewis, the U of T’s associate vice-president of research.

Moreover, the university has been using fewer primates “because of the cost, the availability and the ethics,” said university veterinarian Dr. George Harapa.

It was ethical concern that prompted five U of T graduate students in primatology to try to spare these monkeys from death last week and have them sent to a primate sanctuary such as Story Book Farm, near Sunderland northeast of Toronto, a sort of retirement home for monkeys.

“I was surprised by the nature of the experiment — it sounded like a horror movie; stimulating parts of the brain to see how the monkeys react,” said PhD student Erica Tennenhouse, who co-wrote a passionate letter to university officials last week asking that the two animals be spared and no further primates be used for research.

They learned the animals were already dead, euthanized by lethal overdose of anesthetic for the final stage of the study.

“I was disappointed. These are creatures capable of enjoying a compassionate retired life even after years of trauma,” said graduate student Amber Walker-Bolton, who learned about the experiment at a training course she attended before going to Madagascar to study ring-tailed lemurs.

Yet neuroscientist and dentist Dr. Barry Sessle, who led the study, insisted the primates were not subjected to pain, nor restrained for up to 12 hours at a time, as students had charged.

“It wasn’t pain research and the animal doesn’t feel the electric stimulation from the electrodes because brains aren’t sensitive,” said Sessle.

“Most of the pain research I do is on sub-primates (rodents) and they’re anesthetized.”

He will continue to do monkey studies in partnership with a lab in Chicago.

The monkey study inserted electrodes into the cerebral cortex to unveil a treasure trove of cellular secrets about how the mind adapts when the face is changed due to injury, stroke or even the loss of teeth.

“One of the advantages of using monkeys is that they are intelligent so we can train them to do something and then study how they learn how to do it — we had them learn to protrude their tongue, for example, in a particular position — which gives us knowledge we can use to help improve therapeutic approaches,” said Sessle.

Post-mortem analysis is a crucial piece of the puzzle, he added.

Of some 50,000 vertebrates used each year for scientific research at the U of T, about 85 per cent are mice and rats, thanks to new imaging technology and miniaturization, said Harapa. The rest are mostly fish, plus a few rabbits.

“We stopped using dogs and cats a few years ago too. We can do so much research now by genetically modifying a mouse,” said Harapa.

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“Under a sector microscope you would hardly know the difference between a human heart and that of a mouse.”

The university uses half as many animals in research as it did in the 1980s, Harapa said.

That’s good news for Tennenhouse. “I’m thrilled to hear there will be no more primate research and I hope other universities follow our lead.”