Dynorphin, an endogenous opioid, counteracts endorphins and is involved in thermoregulation, increasing to cool the body when heat rises.

“I started reading about heat stress, and I came across the dynorphin pathway which is an endogenous opioid that we make in our brains, sort of the counter to endorphin because it sort of makes you feel dysphoric rather than euphoric. And then I started reading about how dynorphin actually is a part of the...both endorphin and dynorphin are part of the thermoregulatory pathway. So dynorphin actually cools the body down. And when your body heats up, you increase dynorphin to cool it down. It's sort of a response mechanism.”