Rat research promising for Prozac-takers

by Alison Ramsey

When McGill PhD candidate James Cantor dreamed up a way to eliminate the most troubling--but least publicized--side effect of anti-depressants such as Prozac, he couldn't test his theory on humans. It was too new for clinical trials.

Cantor theorized that a chemical called oxytocin would restore male orgasms and perk up flagging sex drives. A debilitated sex drive is a common complaint among Prozac users that isn't mentioned in company literature.

He brought his theory to his research supervisor, psychology professor Irv Binik, who told him it should be tried on animals. Binik thought immediately of a Concordia colleague, Professor Jim Pfaus of the Centre for Studies in Behavioural Neurobiology. The two professors had been talking off and on for a number of months because they shared a professional interest. "He builds animal models of some of the things I study in humans," explains Binik.

In the summer of 1995, Cantor contacted Pfaus, who was both pleased and surprised to hear from him. "Most clinical students aren't eager to pursue basic biological research," says Pfaus. "For a clinical student to be interested in physiology and mechanisms is extraordinary."

Cantor, who is studying and interning in sex therapy, happened upon his theory while exploring the physiology of sex addiction. He recalled an article in a men's health magazine about oxytocin, which contributes to the blissful feeling that accompanies orgasm. It occurred to him that chronically elevated serotonin levels produced by Prozac might lower oxytocin levels. This, he theorized, could be responsible for dulling the sex drive and even eradicating orgasms among Prozac users.

McGill PhD candidate James Cantor and Concordia professor Jim Pfaus [ PHOTO: OWEN EGAN ]

Binik recalls that there was a lot of anecdotal evidence that Prozac dramatically curbed the sex drive, but no one was really talking about oxytocin at the time. "Potentially, it's a brilliant idea," he remembers thinking.

By September, Cantor and Pfaus had ordered the test rats and spayed the females for the first experiment so that pregnancy wouldn't interfere with their reproductive cycles.

For Cantor, moving from humans to rats was novel. "I thought I'd be injecting animals and watching what they do," says Cantor. "Instead, I had to learn how to do surgery on female rats so they don't get pregnant. I had to know a lot of chemistry--whether a chemical we're using dissolves in oil or water, how and where to inject so it's not absorbed by the liver or other organs, that you have to keep the estrogen supply in the dark--so many little details I had to keep track of."

For weeks the rats were given daily injections of Prozac. As in humans, copulation declined, then stopped. One day, Cantor injected the oxytocin. Within an hour the rats were back to normal.

"I came tearing down the stairs yelling, 'It worked! It worked!" says Cantor, laughing.

A more elaborate experiment with control and comparison groups, requiring Cantor to review 256 hours of videotape of copulating rats ("lots of Ethel Merman--anything to keep me awake"), confirmed the early finding. "Oxytocin corrects the piece of the circuit that interferes in the first place," he said.

The knowledge in itself is of value, but Cantor is more excited about the very real possibility his breakthrough results will be duplicated in people. A few things give him hope that serotonin-induced impotence and flagging sex drive can be cured, perhaps in the near future.

First, the dose of oxytocin required to get the desired effect in rats is very low. Second, oxytocin in high doses has long been approved for human use for such things as inducing labour. Third, the sexual behaviour of male rats is similar to that of male humans. "The males are always ready for sex and will copulate under almost any circumstances," explains Cantor.

Cantor and Pfaus, together with Binik, are preparing to write up the results of both experiments for submission to a scientific journal in the spring. Pfaus expects the article will cause a splash in the medical community.

One of Cantor's next steps--after receiving his PhD--will be to seek permission for clinical trials. Binik agrees that, in principle, clinical trials should be approved. However, he adds, "In practice, when you go to the ethics committee and you say the word 'sex' and the word 'drugs' and the word 'intervention,' you don't know what will happen."

Pfaus is proud of his McGill protégé. "James is a true scientist," he says. "When you say something to him, he doesn't just believe it--he really thinks about it. There's a light between those two eyeballs."