Roles of hypothalamic subgroup histamine and orexin neurons on behavioral responses to sleep deprivation induced by the treadmill method in adolescent rats

Sleep deprivation induces several negative effects on behavior, emotion, attention, and learning ability. Sleep appears to be particularly important during adolescent brain development. In the present study, we examined the effects of sleep deprivation on behavior and hypothalamic neurotransmission including histamine and orexin neurons in adolescent rats using the treadmill method. Adolescent male rats were divided into three groups: treadmill sleep-deprived, treadmill control, and cage control groups. Energy expenditure, anxiety-like behavior, and locomotor activity were examined among the three groups. Histamine concentration in the cortex and diencephalon and the number of c-Fos-positive neurons in the hypothalamus were also examined. In addition, histamine and orexin neurons in the hypothalamus were simultaneously identified using rat histidine decarboxylase and orexin-A immunohistochemistry, respectively. Both energy expenditure and anxiety-related behavior significantly increased by the experimental 3-day sleep deprivation, while exploratory locomotor activity significantly decreased. Histamine contents did not change in the cortex, but significantly decreased in the diencephalon of sleep-deprived rats. Increased expression of c-Fos-positive neurons, including subgroup histamine and orexin neurons, was observed in the hypothalamus. These findings indicate that sleep deprivation increases energy expenditure and anxiety in adolescent rats and provide evidence for the pivotal role of hypothalamus subgroup histamine and orexin neurons in the behavioral response to sleep deprivation.