Pheromones

Have you ever wondered why some people appears more sexually attractive and seductive than others, especially when you get closer to them? Scientists explain that all mammals secrete a chemical substance, called pheromones that is responsible for sexual attraction.

What Should You Know About Pheromones?

Sense of smell is the principal factor that stimulates intuitive responses in animals, and help them in deciding how to react to predators, rivals and potential mates. Kazushige Touhara is a professor at the University of Tokyo's Graduate School of Agricultural and Life Sciences in Japan. Prof. Touhara and his team conducted a research on mice to analyze how male pheromones intensify sexual behavior in females.

Prof. touhara suggested that chemicals, more specifically odors can have a remarkable influence on the instinctive behaviors of animals, even on the first interaction. It is assumed that there are certain neural mechanisms that connects important sensory information to the relevant behavioral centers located inside the brain. Studying this mechanism can be helpful to understandthe reproductive behavior in humans.

The research team focused on exocrine gland-secreting peptide 1 (ESP1), a male pheromone which has been previously indicated as a stimulator of sexual behavior in female mice and aggressive behavior in male mice.

ESP1 is perhaps the only chemical that connects with a single receptor. This one to one contact makes it standout among other pheromones for study and research purposes.

To observe transmittance of ESP1 signals in to the brain, researchers virally infected ESP1 receptor neurons and marked them with fluorescent proteins. Observations indicated that the transfer of signals in to amygdala was different in male and female mice. Amygdala is a component of brain’s limbic system, respons

ible for emotional behaviors and incitements. A sub-area within the amygdala functions as a switch that transmits ESP1 information to various parts of hypothalamus, according to the gender of mice. In male mice, the signals are transferred from peripheral receptive organ to the motor-regulating midbrain, through amygdala-hypothalamus axis. Whereas in females, the sexual behavior was regulated through a different pathway from hypothalamus to the midbrain.

Hypothalamus is a part of brain that releases hormones to regulate numerous body functions such as, sexual drive, mood, thirst, hunger, sleep and body temperature.

The research study also suggested that activation of ESP1 receptor neurons in hypothalamus even in the absence of ESP1 can elevate sexual activity in female mice.

ESP1 And Predator Neurons

To identify the response of receptor neurons against a predator cue signal, researches introduced skin of a snake in the brain's dorsal ventromedial hypothalamus, an area linked to the defensive behavior. No significant change was observed in the sexual behavior after the stimulation of neurons (in reaction to the predator cue signals). This finding suggests that ESP1 and predator cue neurons are two different neurons and only ESP1 is responsible for sexual attitude in female mice.

Although, this research gives a basic idea about how brain circuits turn chemical signaling into sexual and aggressive behaviors in female and male mice, respectively but, an extensive study is required to better understand working and regulation of female sexual behavior. To be specific, a deeper research may provide a strategy to turn male pheromones into sexual retaliation from females. It may also help in determining the sexual dysfunction.

References

• Hattori, T., Osakada, T., Matsumoto, A., Matsuo, N., Haga-Yamanaka, S., Nishida, T., ... & Kikusui, T. (2016). Self-exposure to the male pheromone ESP1 enhances male aggressiveness in mice. Current biology, 26(9), 1229-1234.
• Yoshinaga, S., Sato, T., Hirakane, M., Esaki, K., Hamaguchi, T., Haga-Yamanaka, S., ... & Terasawa, H. (2013). Structure of the mouse sex peptide pheromone ESP1 reveals a molecular basis for specific binding to the class C G-protein-coupled vomeronasal receptor. Journal of Biological Chemistry, 288(22), 16064-16072.