Ventromedial nucleus of the hypothalamus

Structure

It has four subdivisions:

• Anterior (VMHa)
• Dorsomedial (VMHdm)
• Ventrolateral (VMHvl)
• Central (VMHc)

These subdivisions differ anatomically, neurochemically, and behaviorally.

Function

The ventromedial nucleus (VMN) is most commonly associated with satiety. Early studies showed that VMN lesions caused over-eating and obesity in rats. The interpretation of these experiments was questioned when Gold reported that precision-lesioning the VMN did not result in hyperphagia. Nevertheless, numerous studies have shown that the immediacy of hyperphagia and obesity syndrome are a consequence of VMN lesions or procaine injections, and point to the VMN's role in satiety. A major review of the subject in 2006 concluded that, "anatomical studies done both before and after Gold's study did not replicate his results with lesions, and in nearly every published direct comparison of VMH lesions vs. PVN or VNAB lesions, the group with VMH lesions ate substantially more food and gained twice as much weight." This strongly substantiates the classification of VMN as the primary satiety center in the hypothalamus.

It has also been found that lesions to the VMH in rats caused increased plasma insulin levels. Rats with a VMH lesion overproduce a circulating satiety factor (leptin) compared to normal rats, to which the control rats can respond but rats with a VMH lesion cannot, causing them to overeat (leading to obesity).

Researchers looked at a series of twenty-one animals of various degrees of adiposity, with respect to growth appearance, fat distribution, general physical condition, and the correlation between the level of adiposity attained and the correlation of the hypothalamic lesion. Lesions in the hypothalamic area, particularly the region of the ventromedial hypothalamus interrupts a large number of the descending fibers from the hypothalamic cell groups that were found to contribute to obesity in rats.

Another study found that there seems to be a higher concentration of cannabinoid receptor mRNA within the VMH in comparison to other nuclei within the hypothalamus. The cannabinoid ingestion has been linked to rewarding processes, and also with the release of dopamine in the brain.

VMH is also important in mammal play behaviour. Lesions to VMH along with the hippocampus, amygdala, the cerebellum, and the lateral hypothalamus are all linked to reduced play.

The VMHdm has a role in the male vocalizations and scent marking behaviors.

The VMHvl contains many distinct neuronal populations that contribute to varying, often distinct, functions. Notably, this region plays a role in sexual behaviors in females (lordosis), thus stimulating their sexual arousal. The VMHvl has also been found to play a role in estrogen-mediated movement and energy expenditure/thermogenesis.

Bilateral FOS expression in the VMH after repeated seizures is associated with alteration in the severity of flurothyl induced seizures in C57BL/6J mice that are not present in DBA/2J mice. Moreover, bilateral lesions of the VMH are able to block the propagation of seizure discharge to enter the brainstem seizure system.

Surgery

In West Germany, at least 70 men had their VMN operated on between 1962 and 1979. Most of these individuals had been involuntarily institutionalized or imprisoned for deviant sexual behavior, such as homosexuality, perceived hypersexuality among heterosexual men, and pedophilia. This surgery was not commonly performed elsewhere.

References

References

1. (December 2007). "The neonatal ventromedial hypothalamus transcriptome reveals novel markers with spatially distinct patterning". The Journal of Neuroscience.
2. (November 1973). "Hypothalamic obesity: the myth of the ventromedial nucleus". Science.
3. (June 1970). "Feeding patterns of normal and ventromedial hypothalamic lesioned male and female rats". Journal of Comparative and Physiological Psychology.
4. (February 1974). "Inhibitory controls of feeding by the ventromedial hypothalamus". The American Journal of Physiology.
5. (September 1979). "Changes of insulinemia, glycemia and feeding behavior induced by VMH-procainization in the rat". Brain Research.
6. (December 1946). "A study of the effect of hypothalamic lesions on the eating habits of the albino rat". The American Journal of Physiology.
7. (December 1960). "Reciprocal changes in feeding behavior produced by intrahypothalamic chemical injections". The American Journal of Physiology.
8. (November 1975). "Effect of ventromedial hypothalamic procaine injections on feeding, lever pressing, and other behavior in rats". Journal of Comparative and Physiological Psychology.
9. (June 1980). "Time course of feeding induced by pentobarbital-injections into the rat's VMH". Physiology & Behavior.
10. (February 2006). "The rise, fall, and resurrection of the ventromedial hypothalamus in the regulation of feeding behavior and body weight". Physiology & Behavior.
11. (March 1997). "Pathophysiological significance of the obese gene product, leptin, in ventromedial hypothalamus (VMH)-lesioned rats: evidence for loss of its satiety effect in VMH-lesioned rats". Endocrinology.
12. (June 1942). "The relation of various hypothalamic lesions to adiposity in the rat.". Journal of Comparative Neurology.
13. (November 2001). "Anandamide administration into the ventromedial hypothalamus stimulates appetite in rats". British Journal of Pharmacology.
14. (1984). "The psychobiology of play: theoretical and methodological perspectives". Neuroscience and Biobehavioral Reviews.
15. (June 2006). "Co-localization of midbrain projections, progestin receptors, and mating-induced fos in the hypothalamic ventromedial nucleus of the female rat". Hormones and Behavior.
16. (October 2005). "Microlesions of the ventromedial nucleus of the hypothalamus: effects on sociosexual behaviors in male rats". Behavioral Neuroscience.
17. (January 2020). "Selective sexual differentiation of neurone populations may contribute to sex-specific outputs of the ventromedial nucleus of the hypothalamus". Journal of Neuroendocrinology.
18. (May 1998). "Mapping of neural and signal transduction pathways for lordosis in the search for estrogen actions on the central nervous system". Behavioural Brain Research.
19. (1977). "Effects of hypothalamic and preoptic lesions on reproductive behavior in male rats". Brain Research Bulletin.
20. (March 1979). "Facilitation of the lordosis reflex of female rats from the ventromedial nucleus of the hypothalamus". The Journal of Physiology.
21. (September 2000). "Acceleration of mounting behaviors in female rats by ibotenic acid lesions in the ventromedial hypothalamic nucleus". Neuroscience Letters.
22. (January 2015). "An Estrogen-Responsive Module in the Ventromedial Hypothalamus Selectively Drives Sex-Specific Activity in Females". Cell Reports.
23. (April 2020). "Hypothalamic estrogen receptor alpha establishes a sexually dimorphic regulatory node of energy expenditure". Nature Metabolism.
24. (January 2015). "Spatiotemporal differences in the c-fos pathway between C57BL/6J and DBA/2J mice following flurothyl-induced seizures: A dissociation of hippocampal Fos from seizure activity". Epilepsy Research.
25. (March 2017). "Dissociation of spontaneous seizures and brainstem seizure thresholds in mice exposed to eight flurothyl-induced generalized seizures". Epilepsia Open.
26. (November 1998). "The role of the ventromedial nucleus of the hypothalamus in epileptogenesis". NeuroReport.
27. (1979). "Psychosurgery on sex offenders and sexual ?deviants? in West Germany". Archives of Sexual Behavior.