The neuronal networks in the brain that affect rats’ thermoregulatory behaviors have been uncovered by a research team from Nagoya University Graduate School of Medicine in Japan. All animals engage in thermoregulatory activities, which are behavioral mechanisms used to adjust body temperature in response to environmental changes.
These findings, which were reported in the Journal of Neuroscience, help us understand the brain’s neuronal network and offer fresh ideas for treating heat stroke.
Even when the ambient temperature is considerably different, all animals, including humans, use thermoregulatory behaviors to keep their body temperatures within specified ranges. Finding warmer or colder areas and altering posture are some strategies. A turtle lying in the sun or a person who utilizes air conditioning while donning shorts and a t-shirt in the summer are two more concrete instances.
In a previous study, a research group at Nagoya University reported that thermoregulatory behavior requires a region of the brain called the lateral parabrachial nucleus (LPB). The group included Nagoya University graduate student Takaki Yahiro, Lecturer Naoya Kataoka, and Professor Kazuhiro Nakamura.
The same researchers discovered two distinct groups of neurons in the LPB that send thermosensory data from skin thermoreceptors to various regions of the forebrain in a new study.
The two groups of neurons were found to form distinct thermosensory pathways. The first group transmits a warm and cold sensation to a region called the median preoptic nucleus (MnPO). Meanwhile, the other group transmits only a cold sensation to the central nucleus of the amygdala (CeA).
Deep within the temporal lobe of the brain, the amygdala plays a key role in processing and regulating a variety of emotions, including anxiety, fear, and threat reaction. But scientists were unaware that it also played a role in thermoregulatory behavior.
The Nagoya University researchers suspect that the neural pathways they identified form unpleasant emotions to drive thermoregulatory behaviors. Their findings may contribute to a better understanding of the causes of heat stroke and hypothermia.
Some people’s brain pathways may not react negatively to hot and cold stimuli by forming unpleasant emotions. As a result, even when the temperature changes outside, they could not react.
To test this possibility, the researchers blocked one of the thermosensory pathways from the LPB in rats. When the pathway to MnPO was blocked, rats did not avoid heat, leading some to experience increases in body temperature above the normal range. In contrast, blocking the pathway to the CeA abolished the rat’s behavior to avoid cold.
A similar process may occur in humans, especially among older adults. According to Nakamura, “As people age, the generation of heat and cold discomfort through the LPB may be weakened due to the reduced temperature sensitivity of the skin’s thermosensors. This may cause them to fail to perform their thermoregulatory behavior.”
As a result, elderly individuals should refrain from basing their thermoregulatory behavior on irrational elements like emotions. They should instead react to measurable variations in air temperature and humidity. For example, a person should move somewhere cooler based on thermometer and hygrometer readings in the summer, even when not experiencing discomfort.
