Thermoregulatory roles of preoptic area histamine H1 receptor-expressing neurons

The preoptic area (POA) plays a crucial role in regulating body temperature in animals through various thermoregulatory functions. Histamine, a neurotransmitter, is known to influence body temperature across different species, including mammals, lower vertebrates, and invertebrates. The histamine H1 receptor, encoded by the gene Hrh1, is expressed in specific neuronal populations within the POA, with limited overlap among other POA thermoregulatory neurons.

When these POAHrh1 neurons are activated, body temperature and physical activity increase. Conversely, when they are inhibited, the dark phase increase in body temperature is reduced, but physical activity remains unaffected. However, inhibition does not impact body temperature during the light phase, fever, cold exposure, or warm exposure. Behavioral thermoregulation assessments show that POAHrh1 neurons promote nest building in both male and female subjects, potentially contributing to cold-induced nesting behavior.

The POAHrh1 neurons exert their effects on body temperature and physical activity through projections to several hypothalamic nuclei, including the arcuate, dorsomedial, and tuberomammillary nuclei. In summary, POAHrh1 neurons are involved in multiple thermoregulatory processes, including the regulation of daily body temperature rhythms, modulation of physical activity, and the promotion of nest building behavior.