A research study, at the Stowers Institute for Medical Research, has identified the functions of two classes of pheromone receptors. According to the research, the pheromones crucially trigger the mating process in mice.
The researchers have found that one class of receptors helps a male mouse to detect pheromones which indicate the presence of a female. On the other hand, the second class of receptors lets the mice detect if the female mouse is ovulating and ready to mate. As per the study, both sets of pheromones work critically to trigger the process of mating.
The scientists at the Stowers Institute believe that the mice have developed this system through evolution in order to maximize the chance of their reproductive success. This is the reason that the male mice showed great interest in courting and mating with the female in the presence of both pheromones.
The findings of the study were published in the Journal eLife. It offers new insight into how the mammalian brain develops sensory information like pheromones to bring out courtship behaviors. Note that the brain works similarly in mice and humans. Thus, the findings of the study could also increase the understanding regarding inborn behaviors in humans. These behaviors come naturally and don’t have to be learned. Inborn behaviors include seeing, smelling and sexual arousal.
Pheromones potentially trigger many of the inborn behaviors. They are chemical signals that stimulate social responses in others of the same species. These signals let an animal know when a suitable mate is nearby. Moreover, it stimulates the release of hormones that encourages the animal to mate. The vomeronasal organ in the mammals, located between the roof of the mouth and the nose, detects the pheromones.
Mammals have a similar mechanism to control inborn behaviors
The vomeronasal system no longer functions in humans. However, the mechanisms that control our inborn behavior are similar to those in other mammals. For example, the presence of an attractive member, from the opposite sex, stimulates hormonal changes in humans that cause sexual arousal.
The scientists studied the vomeronasal system in the mouse. It provided them with the information on how the brain associates such sensory input with endocrine changes and behaviors. The vomeronasal organ in the mouse contains more than 300 different receptors. However, only a few of them have been matched with the pheromones they detect.
The body releases pheromones in small quantities thus their receptor pairs have been hard to identify. However, some studies in insects have identified pheromones, their receptors and even some neural pathways that control courtship. However, scientists have very limited knowledge regarding mammals.
These researchers took tissue samples from the vomeronasal organ in mice to find more pairs of pheromone receptors. They developed a novel approach using calcium imaging to analyze the cells and isolate the pheromone receptors. The research team then used the receptors to figure out which urine fraction contains the active pheromones.
The findings of the study report the identification of two previously unknown pheromone-receptor pairs. They suggest two ways by which the brain processes sensory information to trigger mating, and discovers the neural pathways, activating inborn behavior in mammals.
The research team plans to build on their research to identify other pheromones and receptors. Moreover, they intend to map out the neural circuitry that transmits information from the vomeronasal organ to the brain. They’re hoping to understand how mammalian brains integrate multiple pieces of information to make critical decisions in their lives.