A potent new spray promotes friendship between animals even, in some cases, if they come from different species, according to a new study.

The spray's active ingredient is oxytocin, which is a naturally occurring hormone released by the pituitary gland. When formulated into a spray, it becomes a veritable Love Potion Number 9, with more emphasis -- at least in this case -- on friendly rather than romantic interactions.

The study, published in the latest issue of the Proceedings of the National Academy of Sciences, looked at how the spray affects dogs, but it holds tremendous promise for human usage too. It might even help to reform curmudgeonly cats.

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"Studies in humans have already shown that oxytocin affects our tendency to affiliate or cooperate with other people," co-author Miho Nagasawa of the University of Tokyo's Department of Cognitive and Behavioral Sciences told Discovery News.

"As far as we know, there are no studies on cats, but we believe that oxytocin is a hormonal mechanism that facilitates the maintenance of close social bonds not only in dogs or cats, but also in any mammal species since the oxytocin system is very ancient and has similar functions in a wide number of taxa," Nagasawa added.

Lead author Teresa Romero, Nagasawa and their colleagues studied how 16 adult dogs of different breeds behaved both with and without being sprayed by the oxytocin formulation. All of the dogs are pets that live with their owners.

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The scientists recorded any instance of bonding behavior that the dogs showed with other familiar dogs as well as with their owners. The behaviors included sniffing, licking, gentle touching with the nose or paw, playing and resting in contact with the other's body. The researchers also measured how much attention the dogs paid to their owners or to their canine pals.

"We found that after receiving the oxytocin spray, dogs displayed more affiliative behaviors and paid more attention to their owners than during the controls," Romero told Discovery News.

As for how the spray works, the researchers said it significantly changed the dogs' heart rate variability and stimulated secretion of oxytocin. These indicate that the spray "can penetrate into the brain and stimulate the oxytocin system in the central nervous system," Nagasawa said.

The hormone is known to play a role in childbirth and lactation, but Romero said that prior studies also show it mediates maternal behavior, mother-infant bonding and pair bonding.

The researchers chose to study dogs, she said, since they are known to form close emotional bonds with each other as well as with another species -- people.

The spray likely won't magically turn enemies into buddies. The researchers said that, when taken as a whole, all of the studies suggest that the effects of oxytocin are context-dependent. The hormone appears to strengthen pre-existing friendships and family connections, but it could stimulate the forging of new beneficial relationships. Romero explained that oxytocin is a promising candidate for treating animal, including human, deficits in social integration.

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Professor Larry Young of the Yerkes National Primate Research Center is director of the Center for Translational Social Neuroscience and is the author of the book "The Chemistry Between Us: Love, Sex and the Science of Attraction."

Young told Discovery News that the new study is "remarkable," in that it "demonstrates for the first time that the same brain chemical that promotes mother-infant bonding and pair bonding between mates/partners is also very likely involved in the bonding between dogs and their owners."

He continued that it's also the first study "to show a neural or chemical mechanism of cross-species bonding."

Young agrees that oxytocin holds great promise for treating people with social impairments, such as autism. He also said that it might also be used to treat previously abused dogs that are distrustful of their new and well-intended human caregivers.