In mammals, fever is a crucial aspect of the immune response to pathogens. The hypothalamus region of the brain contains neurons involved in thermoregulation. When these neuronal circuits are activated by bodily signals released by immune cells during an infection, the core body temperature rises — an event generally referred to as fever.
What’s interesting about ectothermic (colloquially known as cold-blooded) animals, like frogs, is that they do not have this fever response. Instead, they raise their body temperatures by migrating to warmer areas. And, if frogs infected with bacteria are prevented from accessing warmer locations, they are more likely to die. This shows that fever is important for survival during an infection because the internal temperature spike is required to eliminate bacteria from the system.
Some of the major signals produced in the brain during bacterial infection are common between mammals and frogs. One such signal produced in the mammalian brain during infection is prostaglandin. Prostaglandins play a major role in triggering fever in mammals. In fact, one of the ways to suppress fever is by blocking prostaglandin production (which is what ibuprofen does). Directly injecting prostaglandin into the frog brain does not increase body temperature, but it causes the animal to migrate toward areas of higher temperature. This is called behavioral fever.
So, basically, the frog brain, instead of triggering the body to generate heat and have a fever, causes the frog to seek out warmer locations during infections. Our lab is studying how the brain response to infection in tadpoles is altered by external temperature changes. This has important implications for how global warming affects the amphibian immune response to pathogens. At the same time, by examining the mechanisms by which the tadpole brain senses external temperature, we could gain insights into how the mammalian brain adapts to external temperature changes and regulates internal body temperature.
— Anzela Niraula is an assistant professor in neuroscience as well as psychological and brain sciences. Her lab uses mouse models and tadpoles to study the relationship between the immune system and the nervous system.