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Pheromones in new reports

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Pheromones for the young: An article in The Scientist by Jef Akst:

The tears of two- to three-week-old mice contain a pheromone that deters adult males from sexual contact, according to a study published today (October 2) in Nature. In young mice lacking exocrine-gland secreting peptide 22 (ESP22), males made unwanted sexual advances, but painting the compound on the fur of juveniles inhibited this behavior.

“In the past, people actually thought that the lack of [sexual] reaction to young was due to the lack of pheromones. No pheromones, no behavioral responses—that was the common thinking,” said neuroscientist Roberto Tirindelli of the University of Parma in Italy, who did not participate in the study. “Now, for the first time, they show that there is a specific pheromone which is actually active, preventing sexual contact. The inhibition of sexual contact is due to the presence of this pheromone and not to the absence of other pheromones.”

In the last several years, researchers have begun to identify more and more putative pheromones in mice. Specifically, three large gene families, including ESPs, have been recognized to activate the vomeronasal organ (VNO), an olfactory structure located just above the roof of the mouth. But identifying the functions of these dozens of compounds has proven much harder. The first study to link an ESP to function, for example, was published in 2010, when the University of Tokyo’s Kazushige Touhara, an author on the present study, and colleagues found that ESP1 induces lordosis, a sexually receptive posture in females.

Interested in better characterizing the growing number of compounds that may be mouse pheromones,Stephen Liberles’s lab at Harvard Medical School developed a screen to look for differential expression of pheromone homologs across mice, already identifying a predator odor found in carnivores that causes an avoidance response, and an attractive mouse odor. But when the researchers identified a compound that was expressed almost exclusively in juvenile mice, they were intrigued.

Without any preconceived notion of what a juvenile compound might be doing, Liberles’s group “took a Jane Goodall-inspired approach, where we just observed the behavior” of adult males with young mice. . .

Continue reading.

And pheromones in general: Another article in The Scientist, this one by Ron Yu:

Following a trail of smell, a male fruit fly zeroes in on a banana peel. For the fly, the banana is not only a fantastic food source, but also fertile ground for finding mates. Sure enough, a virgin female is already feasting on the banana peel. He approaches her, taps her with his forelegs, and flutters his wings to sound a staccato love song, all in the hopes of securing her as a mate. But there is more to this scene than meets the eye or ear. The success of this courtship ritual critically depends on a single substance: an organic ester, 11-cis-vaccenyl acetate (cVA). CVA is found on the male’s cuticle, or exoskeleton, and in his ejaculatory bulb, a structure similar in anatomy and function to the human prostate. To mature female fruit flies, cVA is an aphrodisiac that induces their receptivity to an approaching male. To males, however, cVA is an antiaphrodisiac, even capable of inducing aggression. Although females do not produce the compound, residual cVA transferred from previous mating partners during copulation remains on their bodies. If a female reeks of the compound, new suitors are repelled.

CVA is a pheromone, classically defined as a substance secreted by an animal that elicits a specific reaction in other members of the species. Although best understood in insects, pheromones are also known to play important roles in mammalian behavior and physiology, from territorial marking in mice to the induction of mating in elephants.

The powerful effect a pheromone can exert on an animal captures the popular imagination. The idea of irresistibility is so ingrained in our psyche that the mention of pheromones immediately conjures up images of love potions, whiffs of which instantly make the wearer more sexually attractive. Indeed, Googling “human pheromone” will lead you to companies trying to sell you one of these “scientifically proven” attractants. (See “Something Smells Funny.”) While such marketing has deepened the sensual mystique surrounding pheromones, so far there is no substantial evidence that such perfumes can induce mate-seeking behavior in men or women. However, decades of research have revealed a fascinatingly wide range of pheromones across the animal kingdom that are not limited to affecting reproductive behaviors. And in the last 10 years or so, scientists have unveiled some of the neural mechanisms of pheromone processing in the brains of both fruit flies and mice, identifying clues to how these compounds work at the molecular, neural, and behavioral levels.

Lessons from the fly

Thanks in part to the fantastic genetic tools developed in the last decade, research on the fruit fly, Drosophila melanogaster, has uncovered many details of pheromone pathways, from the antennae to the brain. CVA, the only volatile fly pheromone so far identified, is detected in the antennae by olfactory receptor neurons (ORNs) that express a G protein-coupled receptor called OR67d. These neurons project their axons into bulb-shape structures called glomeruli in the antennal lobe of the brain, where olfactory information is initially processed. Each glomerulus is innervated by a distinct set of projection neurons (PNs) that then transmit the information into deeper brain regions. (See “Odor Encoder.”)

How does cVA, a single compound emitted by male flies, trigger behaviors that differ so widely between males and females?

Continue reading.

Written by Leisureguy

10 October 2013 at 8:58 am

Posted in Science

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