An interesting new study has pointed out to existence of a substance that could have the potential application of rodent control without the need to use rodent killing chemicals.
Researchers at University of Tokyo have discovered a substance in young mice’s tears that they say makes female mice more likely to reject male sexual advances. Direct connections between human and mouse behavior cannot be made because pheromones are highly species specific.
Researchers hope to use the tear pheromone as a natural mouse birth control to reduce mouse populations in the future. If the substance is used in rodent control applications, it is unlikely that other animals would be affected because pheromones are so species specific. The sex-rejecting behavior is an innate instinct, so it’s also unlikely that the mice will learn to change their behavior or ignore the artificial pheromone.
Only juvenile mice aged one to three weeks produce the pheromone, called exocrine gland-secreting peptide 22 (ESP22). ESP22 is not airborne and lacks a noticeable odor, but the pheromone spreads around the territory as mothers and young mice wipe tears while grooming.
Both mothers and virgin female mice reject male sexual advances after exposure to ESP22. Less female interest in sex would theoretically benefit juvenile mice by reducing the number of younger siblings competing for resources.
ESP1 is an adult male pheromone that was previously studied for its role in enhancing female acceptance of sex. In this new study, researchers tracked how ESP22 and ESP1 are received and processed by the adult female mouse brain. Pheromone signals from young mice overrode the signals from adult males. Virgin female mice rejected male advances when they were exposed to the sex-rejecting ESP22 even after being exposed to the sex-accepting ESP1.
Both sex-rejecting ESP22 and sex-accepting ESP1 pheromones are recognized by single, dedicated receptors in the nose. Specific neurons send the different pheromone signals to the brain. The presence of similar but specific ESP1 and ESP22 receptors helps reveal how animals evolved the ability to detect and interpret pheromone signals.
Pheromone signals are routed to the medial amygdala, a small group of neurons in the brain.
ESP22 and ESP1 signals travel separately but in parallel until reaching the medial amygdala. After that point, the pheromones affect different neurocircuitry in the brain to create different behaviors. Ongoing research in the laboratory will explore pheromone-related neurocircuitry beyond the medial amygdala hub.