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.

（應(yīng)該指的是ventromedial hypothalamus活動導致the feeling of fullness。從而不再吃或者動。那么很有可能ventromedial hypothalamus用的是抑制型軸突。也有可能是通過cannabinoid遞質(zhì)反向抑制orexinergic neuron導致的滿足感，畢竟lateral hypothalamus能夠激發(fā)所有五種彌散系統(tǒng)。有可能內(nèi)啡肽與cannabinoid同時發(fā)生，一個抑制了疼痛系統(tǒng)與NE彌散系統(tǒng)，另一個抑制了lateral hypothalamus。the caudal ventrolateral PAG似乎與ventromedial hypothalamus同時活動，這意味著進入satiety狀態(tài)時，caudal ventrolateral PAG活動，ventromedial hypothalamus活動，這樣的話dorsal and lateral aspects of the PAG就被抑制，同時ventromedial hypothalamus似乎反向釋放cannabinoid從而抑制orexinergic neuron，即抑制lateral hypothalamus，在這里存在caudal ventrolateral PAG投射到ventromedial hypothalamus的連接關(guān)系。Satiety狀態(tài)應(yīng)該是caudal ventrolateral PAG活動從而帶動ventromedial hypothalamus活動，抑制了dorsal and lateral aspects of the PAG和lateral hypothalamus，從而減少了交感系統(tǒng)的活動，允許副交感系統(tǒng)強烈活動，從而讓組胺能彌散性調(diào)節(jié)系統(tǒng)強烈活動而抑制大腦皮層、nucleus accumbens和dorsal striatum，從而減少主動行為，此時VTA不被nucleus accumbens抑制，杏仁核活動減少，那么就會通過pontine Ach system來興奮VTA，此時胃腸內(nèi)容物多，也會通過solitary nucleus去興奮血清素、抑制NE，差不多satiety的狀態(tài)下會發(fā)生這些事情吧。要注意的是，如果VTA過于興奮，就會通過nucleus accumbens活動去一定程度抑制下丘腦中的組胺能彌散性調(diào)節(jié)系統(tǒng)，從而減少副交感系統(tǒng)的活動，同時疼痛信息也可以直接投射興奮VTA，所以疼痛是可以抑制食欲的。satiety狀態(tài)的本質(zhì)是副交感系統(tǒng)過于活躍同時caudal ventrolateral PAG過于活躍的結(jié)果，而agranular BA11皮層是可以直接投射到PAG，即BA11中存在投射caudal ventrolateral PAG和dorsal and lateral aspects of the PAG，也就是說可以通過意識來一定程度調(diào)控satiety狀態(tài)和調(diào)控疼痛信息的傳遞。

但是根據(jù)另一篇文章內(nèi)容，如果只興奮ventromedial hypothalamus，就會導致本來不暴力的小鼠開始出現(xiàn)間斷性的暴力行為?？匆曨l似乎是小鼠克制不住自己的狀態(tài)而間斷性地對另一只安靜的小鼠攻擊，我覺得原因在于只用電極刺激ventromedial hypothalamus，其作用應(yīng)該是反向抑制了lateral hypothalamus，而此時caudal ventrolateral PAG不活動，那么就不能對dorsal and lateral aspects of the PAG進行抑制，那么DA放大環(huán)路就會工作從而強烈興奮DA系統(tǒng)，

差不多ventromedial hypothalamus的功能也弄清楚了，要和lateral hypothalamus、caudal ventrolateral PAG有很大關(guān)系，也和副交感系統(tǒng)的活動有關(guān)系。

小總結(jié)一下吧，BA11能夠直接投射到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。這些皮層，可以很大程度改變相應(yīng)核團的輸出，也就是說可以改變NE放大環(huán)路、DA放大環(huán)路等環(huán)路的運作情況。以前一直只認為anterior insular cortex與anterior cingulate cortex很重要，現(xiàn)在發(fā)現(xiàn)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這個現(xiàn)象與leptin實驗結(jié)果相似，即少了對lateral hypothalamus的抑制，就會導致over-eating and?obesity。這句話暗含的更重要意義是ventromedial nucleus是能夠抑制lateral hypothalamus的，且很有可能是通過cannabinoid遞質(zhì)反向抑制。進食后最大的改變就是血液中成分的改變，可能這就是觸發(fā)cannabinoid合成與釋放的條件。另一個例子是，當因為不吃飯而導致血液成分變得糟糕時，會激發(fā)嗅球中cannabinoid的合成與釋放，所以我覺得在其他結(jié)構(gòu)處cannabinoid的合成與釋放很有可能與血液的質(zhì)量有很大關(guān)系，比如basal ganglia，吃飽的動物，其basal ganglia似乎不太活躍，其motivational behavior也大大減少。而吸食大麻則屬于外來的cannabinoid，可以去對比一下這樣人的行為與satiety狀態(tài)、動力不足的人，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（不是說了嗎，leptin的升高通過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.

（應(yīng)該說VMH接受來自自主神經(jīng)系統(tǒng)器官的信息，而leptin是脂肪細胞釋放的，所以飽腹的器官會促使VMH去反向抑制lateral hypothalamus，過高的leptin也會抑制lateral hypothalamus，當VMH壞掉時，就需要更高的leptin才能達到原有的抑制效果。）?

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.（有些書將arcuate nucleus列為VMN中的一部分，但是本詞條就沒有。）[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.（這些應(yīng)該都和交配有關(guān)吧，就算是female，也會出現(xiàn)為了交配而到處撒尿留氣味和吼叫。）[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]