Japanese scientists have found the mechanism of switching the brain of males

(ORDO NEWS) — Hypothalamic oxytocin neurons have been called a key regulator of nurturing behavior in father mice.

A team of Japanese neuroscientists from the Biosystems Dynamics Research Center at the Institute of Physical and Chemical Research (RIKEN) found that due to the peptide “love hormone” – oxytocin – male mice radically change their attitude towards cubs.

The adult brain has neuroplasticity, which allows it to change behavior in accordance with the specific requirements of life.

Thus, inexperienced animals rarely take care of children of their own species, since such behavior can become a heavy burden and reduce their fitness : for example, an adult male mouse, who has never had contact with females, often attacks and even kills cubs, but can turn into a loving father after the birth of your own child.

Despite a lot of research, the neural mechanisms that cause changes in behavior are poorly understood. The main pathway by which the brain achieves neuroplasticity is thought to be a change in the strength of the synaptic connections between neurons.

But it is difficult to determine exactly which neurons or their types form synapses that undergo changes as a result of a particular event.

Answering these questions requires pinpointing the exact location and type of nerve cells whose synaptic connections change. This was the goal of the authors of the new work, and forced fatherhood served as such a decisive life “turn”.

Previous studies have shown that injections of oxytocin, produced by neurons in the paraventricular nucleus of the hypothalamus, engender care in virgin female rodents. In contrast, loss of oxytocin function or its receptor exhibits only minor maternal nurturing behavior.

In addition, scientists suggest that the action of this hormone may contribute to the onset of care, but to a lesser extent, its maintenance.

However, in contrast to the experiments with females, the function of oxytocin in the male brain and the parental nurturing behavior associated with it has been largely overlooked.

And for the first time, Japanese researchers have identified the crucial role of oxytocin-producing hypothalamic neurons in neuroplasticity in male mice when they become parents.

“While women experience many physiological and endocrinological changes in the body, becoming mothers, any neuroendocrinological changes in men were considered subtle or absent.

But we found that oxytocin, a hormone associated with childbirth and lactation, has a strong effect on male mice,” said Kazunari Miyamichi, lead author of the study.

Experiments on mice have shown that forced activation of oxytocin-producing neurons provokes a full set of characteristics of parental behavior in males, first suppressing their habitual propensity for infanticide – infanticide.

“We have shown that activation of oxytocin-producing neurons modulates the activity of several different types of nerve cells: infanticidal PeFA Ucn3+ neurons are downregulated, while MPNm Calcr+ parental neurons are upregulated when virgin male mice encounter pups,” the scientists write.

They admit that this function of oxytocin is also present in humans, since there is a correlation between the level of this “love hormone” in the father’s blood and the intensity of his interactions with the child.

By the way, unlike females, in males, care for the child completely disappeared in the absence of the action of oxytocin or prolactin.

Another unexpected discovery was the very plasticity of neuronal connections in the hypothalamus. “It was believed that the functions of the hypothalamus are mediated by programmed neural circuits that never change.

Our work is one of the few that have demonstrated the functional and structural plasticity of the hypothalamus,” the scientists summed up.


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