wiki笔记--Ventromedial nucleus of the hypothalamus--2022/6/21

Ventromedial nucleus of the hypothalamus

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The ventromedial nucleus of the hypothalamus (VMN, also sometimes referred to as the ventromedial hypothalamus, VMH) is a nucleus of the hypothalamus. "The ventromedial hypothalamus (VMH) is a distinct morphological nucleus involved in terminating hunger, fear, thermoregulation, and sexual activity."[1] This nuclear region is involved in the recognition of the feeling of fullness.

（应该指的是ventromedial hypothalamus活动导致the feeling of fullness。从而不再吃或者动。那么很有可能ventromedial hypothalamus用的是抑制型轴突。也有可能是通过cannabinoid递质反向抑制orexinergic neuron导致的满足感，毕竟lateral hypothalamus能够激发所有五种弥散系统。有可能内啡肽与cannabinoid同时发生，一个抑制了疼痛系统与NE弥散系统，另一个抑制了lateral hypothalamus。the caudal ventrolateral PAG似乎与ventromedial hypothalamus同时活动，这意味着进入satiety状态时，caudal ventrolateral PAG活动，ventromedial hypothalamus活动，这样的话dorsal and lateral aspects of the PAG就被抑制，同时ventromedial hypothalamus似乎反向释放cannabinoid从而抑制orexinergic neuron，即抑制lateral hypothalamus，在这里存在caudal ventrolateral PAG投射到ventromedial hypothalamus的连接关系。Satiety状态应该是caudal ventrolateral PAG活动从而带动ventromedial hypothalamus活动，抑制了dorsal and lateral aspects of the PAG和lateral hypothalamus，从而减少了交感系统的活动，允许副交感系统强烈活动，从而让组胺能弥散性调节系统强烈活动而抑制大脑皮层、nucleus accumbens和dorsal striatum，从而减少主动行为，此时VTA不被nucleus accumbens抑制，杏仁核活动减少，那么就会通过pontine Ach system来兴奋VTA，此时胃肠内容物多，也会通过solitary nucleus去兴奋血清素、抑制NE，差不多satiety的状态下会发生这些事情吧。要注意的是，如果VTA过于兴奋，就会通过nucleus accumbens活动去一定程度抑制下丘脑中的组胺能弥散性调节系统，从而减少副交感系统的活动，同时疼痛信息也可以直接投射兴奋VTA，所以疼痛是可以抑制食欲的。satiety状态的本质是副交感系统过于活跃同时caudal ventrolateral PAG过于活跃的结果，而agranular BA11皮层是可以直接投射到PAG，即BA11中存在投射caudal ventrolateral PAG和dorsal and lateral aspects of the PAG，也就是说可以通过意识来一定程度调控satiety状态和调控疼痛信息的传递。

但是根据另一篇文章内容，如果只兴奋ventromedial hypothalamus，就会导致本来不暴力的小鼠开始出现间断性的暴力行为。看视频似乎是小鼠克制不住自己的状态而间断性地对另一只安静的小鼠攻击，我觉得原因在于只用电极刺激ventromedial hypothalamus，其作用应该是反向抑制了lateral hypothalamus，而此时caudal ventrolateral PAG不活动，那么就不能对dorsal and lateral aspects of the PAG进行抑制，那么DA放大环路就会工作从而强烈兴奋DA系统，

差不多ventromedial hypothalamus的功能也弄清楚了，要和lateral hypothalamus、caudal ventrolateral PAG有很大关系，也和副交感系统的活动有关系。

小总结一下吧，BA11能够直接投射到PAG；anterior insular cortex能直接投射到central nucleus of amygdala和intercalated cluster cells of amygdala；anterior cingulate cortex似乎也能直接投射到central nucleus of amygdala和intercalated cluster cells of amygdala。这些皮层，可以很大程度改变相应核团的输出，也就是说可以改变NE放大环路、DA放大环路等环路的运作情况。以前一直只认为anterior insular cortex与anterior cingulate cortex很重要，现在发现BA11也很重要。）

Contents

· 1Structure

· 2Function

· 3References

· 4Further reading

· 5External links

Structure[edit]

It has four subdivisions:

· Anterior (VMHa)

· Dorsomedial (VMHdm)

· Ventrolateral (VMHvl)

· Central (VMHc)

These subdivisions differ anatomically, neurochemically, and behaviorally.

Function[edit]

The ventromedial nucleus (VMN) is most commonly associated with satiety. Early studies showed that VMN lesions caused over-eating and obesity in rats.

（VMN lesions caused over-eating and obesity in rats这个现象与leptin实验结果相似，即少了对lateral hypothalamus的抑制，就会导致over-eating and obesity。这句话暗含的更重要意义是ventromedial nucleus是能够抑制lateral hypothalamus的，且很有可能是通过cannabinoid递质反向抑制。进食后最大的改变就是血液中成分的改变，可能这就是触发cannabinoid合成与释放的条件。另一个例子是，当因为不吃饭而导致血液成分变得糟糕时，会激发嗅球中cannabinoid的合成与释放，所以我觉得在其他结构处cannabinoid的合成与释放很有可能与血液的质量有很大关系，比如basal ganglia，吃饱的动物，其basal ganglia似乎不太活跃，其motivational behavior也大大减少。而吸食大麻则属于外来的cannabinoid，可以去对比一下这样人的行为与satiety状态、动力不足的人，似乎真的有很大相似性。） 

However, the interpretation of these experiments was summarily discredited when Gold's research demonstrated that precision lesioning of the VMN did not result in hyperphagia（不是说了吗，leptin的升高通过arcuate nucleus可以抑制lateral hypothalamus。）.[2] 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.[3][4][5][6][7][8][9] 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."[10] 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.

（应该说VMH接受来自自主神经系统器官的信息，而leptin是脂肪细胞释放的，所以饱腹的器官会促使VMH去反向抑制lateral hypothalamus，过高的leptin也会抑制lateral hypothalamus，当VMH坏掉时，就需要更高的leptin才能达到原有的抑制效果。） 

Rats with a VMH lesion compared to normal rats overproduce a circulating satiety factor, to which the control rats can respond and rats with a VMH lesion cannot respond. A lesion to the VMH makes rats overproduce leptin, which they cannot respond to causing them to over eat, leading to obesity.（有些书将arcuate nucleus列为VMN中的一部分，但是本词条就没有。）[11]

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.[12]

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.[13]

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.[14]

The VMHdm has a role in the male vocalizations and scent marking behaviors.（这些应该都和交配有关吧，就算是female，也会出现为了交配而到处撒尿留气味和吼叫。）[15][16]

The VMHvl contains many distinct neuronal populations that contribute to varying, often distinct, functions.[17] Notably, this region plays a role in sexual behaviors in females (lordosis), thus stimulating their sexual arousal.[18][19][20][21] The VMHvl has also been found to play a role in estrogen-mediated movement [22] and energy expenditure/thermogenesis.[23]

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.[24][25] Moreover, bilateral lesions of the VMH are able to block the propagation of seizure discharge to enter the brainstem seizure system.[26]