Why females prefer warmer temperatures than males

NEW DELHI: A study conducted in mice has found that females preferred warmer spaces than males due two temperature sensors in nerves, one for warmth and one for coolness, both of which switch on at higher temperatures.

Female mice preferred a floor temperature of 36 degrees Celsius, compared with 32 degrees Celsius for males. Similarly, women prefer room temperature of around 25 degrees Celsius, while men prefer it around 22 degrees Celsius.

The findings, published in The Journal of Physiology, points to two ion channels behind the preference—tiny pores in nerve cells that open as temperature changes, letting charged particles flood in and ultimately fire a signal to the brain.

Researchers at King’s College London said the channel ‘TRPM2’ picks up gentle warmth, while ‘TRPM8’ picks up coolness. In female mice, both types of channel activate at warmer temperatures than in males.

Therefore, a floor that feels pleasantly warm to a female feels unpleasant to a male, they said.

Peter McNaughton, professor in pharmacology at King’s College London, said while it has long been known that in mammals, including humans, females prefer a warmer environment than males, the molecular basis for this difference had not been identified until now.

“In mice, we found that the thermal ranges of activation of the two ion channels that detect warmth and coolness, TRPM2 and TRPM8, are shifted towards warmer temperatures in females, and it is this shift that causes the difference in how males and females sense and react to temperature,” McNaughton said.

“This study did not look at humans, but humans have both of these types of ion channels, and similar differences in average temperature preference so it is likely that a similar mechanism is at work,” McNaughton added.

The researchers placed mice on two heated metal plates, that could be gently warmed, side by side. One was kept at 33 degrees Celsius and the other was varied, and the team watched which one the mice chose to stand on.

Males were seen to avoid a plate heated to 38 degrees Celsius, while females strongly preferred it.

Genetically removing the warmth sensor shifted males towards preferring warmer temperatures. Removing or blocking the cool sensor shifted females towards cooler ones, the researchers found.

Because a genetic change and a drug that blocked the sensors gave the same result, the researchers concluded that the effect was due to direct actions on the sensors themselves.

Hormones play a part in this process—lowering testosterone in male mice shifted them towards the female preference for warmth, and raising it in females made them more averse to warmth, they said.

However, female sex hormones had no effect, and testosterone did not explain the whole difference.

Body temperature wasn’t the cause either as males and females had the same core and skin temperature, suggesting that the mice were responding to what they felt through their paws, the researchers said.

The authors wrote, “Female thermal preference is shifted to warmer temperatures by around 4 degrees Celsius when compared to males, consistent with warm shifts in the female activation ranges of both TRPM8 and TRPM2.”