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Cholecystokinin B receptor
The cholecystokinin B receptor also known as CCKBR or CCK2 is a protein that in humans is encoded by the ''CCKBR'' gene.
This gene encodes a G protein-coupled receptor for gastrin and cholecystokinin (CCK), regulatory peptides of the brain and gastrointestinal tract. This protein is a type B gastrin receptor, which has a high affinity for both sulfated and nonsulfated CCK analogs and is found principally in the central nervous system and the gastrointestinal tract. A misspliced transcript variant including an intron has been observed in cells from colorectal and pancreatic tumors.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=887 )〕
== CNS effects ==
CCK receptors significantly influence neurotransmission in the brain, regulating anxiety, feeding, and locomotion. CCK-B expression may correlate parallel to anxiety and depression phenotypes in humans. CCK-B receptors possess a complex regulation of dopamine activity in the brain. CCK-B activation appears to possess a general inhibitory action on dopamine activity in the brain, opposing the dopamine-enhancing effects of CCK-A. However, the effects of CCK-B on dopamine activity vary depending on location. CCK-B antagonism enhances dopamine release in rat striatum. Activation enhances GABA release in rat anterior nucleus accumbens. CCK-B receptors modulate dopamine release, and influence the development of tolerance to opioids. CCK-B activation decreases amphetamine-induced DA release, and contributes to individual variability in response to amphetamine.
In rats, CCK-B antagonism prevents the stress-induced reactivation of cocaine-induced conditioned place preference, and prevents the long-term maintenance and reinstatement of morphine-induced CPP. Blockade of CCK-B potentiates cocaine-induced dopamine overflow in rat striatum.〔 CCK-B may pose a modulatory role in parkinson's disease. Blockade of CCK-B in dopamine-depleted squirrel monkeys induces significant enhancement of locomotor response to L-DOPA. One study shows that visual hallucinations in Parkinson's disease are associated with cholecystokinin −45C>T polymorphism, and this association is still observed in the presence of the cholecystokinin-A receptor TC/CC genotype, indicating a possible interaction of these two genes in the visual hallucinogenesis in Parkinson's disease.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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