Darcin (pheromone): characteristics and effect on the brain

The pheromone known as darcin has a function in the reproduction of some animals.

Although humans are animals, there are some Biological mechanisms that are present in many species except ours, and one of them, very important indeed, is the emission of pheromones.

Pheromones can be responsible for activating a wide variety of behaviors and physiological processes, the most important of which is the sexual response. the pheromone known as darcin a particularly important one during rodent reproduction.

This pheromone is named after an attractive character from the romantic Jane Austen, which already suggests its ability to generate a chemical attraction between animals. Let's take a closer look at what this pheromone does and how it influences the brains of certain animals, such as rodents.

Darcyne: pheromones and chemical love.

Jane Austen, famous British writer of the Romanticism, introduced us to Mr. Fitzwilliam Darcya handsome and wealthy young man who romanced the protagonist of Pride and Prejudice (1813), Miss Elizabeth Bennet. While nothing has yet been discovered in humans to give us Darcy's power of attraction over Lizzie, a pheromone has been found in nature that has a similar power in rodents and has been named after this romantic hero: darcin.

Pheromones are airborne chemicals that can have varied behavioral effects in different animal species.. They are specific and are used as a method of communication between individuals of the same species, inducing both behavioral and physiological changes.

Although no such substances have been found in humans so far, in many animals pheromones are mainly responsible for the act of reproduction, darcin being one of them.

The sexual life of mice

Although they are small animals with tiny brains, mice have a surprisingly complex sex life. As with other mammals, including our own species, these small mammals interpret behavioral and olfactory cues in a way that interpret behavioral cues and odors emitted by other individuals of the same species as a signal that they are ready, or not, for mating.. It seems that darcin is a pheromone that plays a major role in this process.

When male mice urinate, in addition to marking their territory, they send a signal that they are looking for a female to mate with. In their urine is found darcin, which will make the female mice realize the availability of the male and, depending on the odor he is emitting, go for him and decide if they want to have his offspring. This act of smelling is not as simple as in our species. Animals that use pheromones have two types of noses, each one fulfilling different functions.

On the one hand, we have the nose, which fulfills the same function as that of humans: to identify odors. It is through this structure that animals are able to detect the pleasant smells of food and go towards it or pestilent smells such as that of dead animals that indicate that their meat cannot be eaten or that we are even close to danger.

But it is the vomeronasal nose, which is not found in our species, that is in charge of perceiving pheromones, such as darcin, and sending the signal to the brain. It is in the animal's brain that the signal will be interpreted and behavior will be orchestrated according to the demands of the environment. If the hormone is of a reproductive type, the animal will initiate behaviors in search of the individual that has given the signal that it is available for mating, as in mice. that it is available for mating, as is the case with mice.

Although the importance of darcin on the sexual behavior of mice was known, it was not until relatively recently that the brain mechanisms that explain this type of behavior were discovered, in addition to understanding the behavioral differences between available female mice and those that have just given birth to still-lactating offspring.

Brain changes

A very recent study, from this same year 2020 and carried out by Ebru Demir's group at Columbia University, discovered the process by which the darcin pheromone influences the brains of female mice.

As we have already seen, it is this pheromone that triggers female mice's sexual desire and predisposition to mate. However, not all female mice, upon smelling male urine, showed pro-mating behaviors. Females that had already recently had pups and were still lactating seemed to ignore those places where males had marked their territory.

The reason for this seems to lie in the medial amygdala of the reddish brain.r. Ebru Demir's group found that this region would contain a subset of neurons, called nNOS neurons, that are activated when darcin is floating in the air. By artificially activating this structure, the researchers found that sexual behaviors were induced, while deactivating these neurons caused the animal to lose interest in mating.

But the nNOS neurons are not simply in charge of the information that has to do with darcin. These neurons are also involved in integrating sensory information about the pheromone with the internal state of the mouse, and whether or not it is nursing pups.

The major finding of this study is that it has disproved a widely held belief about pheromones, namely that they induce a behavioral response that is innate and immediate. In the case of darcin, it induces more complex behaviors, which depend on the state in which the pheromone is present.which depend on the state of the female to whom it is directed, whether it is a lactating mother or a mouse in search of a male.

Bibliographical references:

• Roberts et al., Darcin: a male pheromone that stimulates female memory and sexual attraction to an individual male's odour BMC Biology 2010, 8:75.
• Demir, E., Li, K., Bobrowski-Khoury, N. et al. (2020) The pheromone darcin drives a circuit for innate and reinforced behaviours.Nature https://doi.org/10.1038/s41586-020-1967-8.
• Percy-Cunningham JE, MacDonald JA (1987). «Biology and ultrastructure of sex pheromone-producing glands.». Prestwich GD, Blomquist GJ (eds) Pheromone Biochemistry. Orlando/FL: Academic Press.: 27-75.
• Winman, A. (2004). Do perfume additives termed human pheromones warrant being termed pheromones?. Physiology & Behavior 82 (4): 697-701.
• Moncho-Bogani, J, Martínez-García, F., Novejarque, A., Lanuza, E. (2005). «Attraction to sexual pheromones and associated odorants in female mice involves activation of the reward system and basolateral amygdala.». European Journal of Neuroscience. 21(8) 2186 - 2198.