New York, Feb 5 (IANS): Researchers have identified the protein which offers females stronger protection against brain injury.

It has been known for some time that male infants are more vulnerable to hypoxic ischemic encephalopathy (HIE) - a type of brain injury - than females, but why this gender difference exists has remained a mystery.

This type of brain injury that can lead to long-term neurological issues such as learning disabilities, cerebral palsy or even death occurs due to complications during pregnancy or birth that deprive their brains of oxygen and nutrient-rich blood and result in brain injury.

"People often think that biological sex differences start to arise only after puberty, but they actually start in the womb and persist until the tomb," said lead researcher Pelin Cengiz, associate professor at University of Wisconsin-Madison in the US.

"So, treatment approaches that may work for newborn boys may not work for girls, and vice versa. We need to get it right to develop effective therapies," Cengiz noted.

In this study published in the journal eNeuro, the researchers showed that a protein called estrogen receptor ?, or ER? for short, found in the brains of both male and female mice is present at higher levels in females, which offers them stronger protection against HIE.

When the researchers studied the brains of male and female mice that could make the ER? protein, they learned that levels of this protective protein were significantly higher in female compared to male brains following oxygen deprivation and reduced blood flow.

"Under normal circumstances the brains of male and female mice have similar amounts of ER?," Cengiz pointed out.