Role in the Functional Feeding System
The ventromedial hypothalamus (VMH) is a central structure in the functional system of feeding. It interacts with the lateral hypothalamus (LH), which acts as the "hunger center." The interaction between these two centers shapes feeding behavior.
The process of satiety is divided into two types:
- Sensory satiety — formed during the passage of food through the oral cavity, esophagus, and stomach; it is driven by receptor signals prior to absorption.
- Metabolic satiety — occurs after nutrients are absorbed into the bloodstream and represents true satiety.
Mechanisms Regulating the Satiety Center
In the functional feeding system, the primary regulated parameter is blood nutrient levels.
- Vascular chemoreceptors: monitor nutrient concentrations in the blood and transmit signals to the CNS — specifically to the LH and VMH.
- Hormonal regulation and leptin: leptin is produced by adipose cells (adipocytes). Circulating leptin levels are directly proportional to body fat mass. Leptin receptors are found on many cells, with a key target being the neurons of the ventromedial hypothalamic nucleus. Leptin decreases appetite and increases energy expenditure. Its secretion is pulsatile, peaking at night (24:00–04:00) and reaching its lowest levels in the morning and midday.
Effects of Stimulation and Lesions
The functional role of the ventromedial hypothalamus has been demonstrated in experimental studies:
- Electrical stimulation: leads to the cessation of eating, even in hungry animals.
- Bilateral destruction: animals struggle to finish meals due to a lack of the feeling of fullness, leading to hyperphagia, bulimia ("wolfish hunger"), and subsequent obesity. For comparison: destruction of the lateral regions, which are responsible for hunger, leads to food refusal—aphagia.
- Pharmacological intervention: sibutramine has been used to suppress appetite by acting on satiety mechanisms.
Not to Be Confused: VMH in Neurology
In medical literature, the abbreviation VMH can also stand for ventricular mass hemorrhage or intracerebral hematoma (hematoma intracerebralis). Intracerebral hemorrhage falls under the classification of non-traumatic intracranial hemorrhages in hemorrhagic stroke.
To assess severity and prognosis in intracerebral hemorrhage, the ICH Score is used. It takes into account: the Glasgow Coma Scale score, hematoma volume, presence of intraventricular hemorrhage, infratentorial (subtentorial) origin of the hematoma, and patient age.