Study finds hemoglobin is a chemosensory signal for mother mice to protect pups

A paper describing the researchers' findings has just been published in the journal Nature Communications

Back in 2005, researchers in the laboratory by Kazushige Touhara of the University of Tokyo had discovered in the tears of male mice a chemical secreting a pheromone -- an animal that influences the behavior of others in the same species -- named ESP1 (exocrine secretion).

In subsequent studies to try to pinpoint the source of this neuronal activation, the researchers found that blood-contaminated glands were the culprit

The researchers then first exposed male mice to a small amount of blood and observed blood-dependent activation of peripheral sensory neurons located in the vomeronasal organ of the nose

Even elementary school students, "everyone knows that hemoglobin is a molecule that carries oxygen in the blood, so the discovery that it acts as a chemosensing signal to the nose comes as a real surprise," said Touhara, corresponding author of the paper and a professor at the University of Tokyo.

Mice in their natural environment are exposed to blood under certain conditions, such as injury from aggression between males, injury from attack by predators, and childbirth

Once they found the brain region responsible for hemoglobin signaling, only in nursing mothers did specific neural activations in a region in the hypothalamus that received information from sensory neurons in the vulgaris

"Mothers displayed digging or nurturing behaviors immediately after receiving the hemoglobin after playing with a hemoglobin-soaked cotton swab," Touhara continued

The researchers also found that hemoglobin in the blood stimulates ampulla sensory neurons through a specific receptor, Vmn2r88

Next, by using optogenetics and light and genetic engineering techniques to manipulate neural activity in the hypothalamus, the researchers were able to replicate the digging behavior and thereby propose a neural circuit responsible for regulating these hemoglobin-mediated behaviors

This digging and nurturing represents an exploratory and/or risk-assessing behavior, suggesting that the response to hemoglobin appears to be important for mothers to protect their pups by examining the external environment

From this study, Touhara and his team discovered that a well-known molecule in the blood, hemoglobin, acts as a chemosensory molecule and its receptor circuit mechanism is responsible for a exploratory and/or risk assessment behavior in lactating female puppies rat

Journal Reference :

1. Takuya Osakada, Takayuki Abe, Takumi Itakura, Hiromi Mori, Kentaro K.