The tuberomammillary nucleus (TMN) is a small cluster of nerve cells located in the hypothalamus, a region of the brain that plays a key role in regulating various physiological functions, such as hunger, thirst, sleep, and arousal.
In the context of sleep and arousal, the TMN is involved in the regulation of histamine, a neurotransmitter that promotes wakefulness and alertness. The TMN is the main source of histamine in the brain, and it has a key role in regulating the sleep-wake cycle.
In animal studies, lesioning of the TMN has been shown to cause drowsiness and sleepiness, while stimulation of the TMN can promote wakefulness and alertness. This is why histamine receptor antagonists, also known as antihistamines, which block the action of histamine at its receptors, can cause drowsiness and sedation.
It is important to note that the TMN is part of a complex network of brain regions that work together to regulate sleep and arousal, and that the regulation of these functions is influenced by various internal and external factors, such as hormones, neurotransmitters, and environmental cues.