autoreceptor

• 自己受容体、オートレセプター

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/18 10:08:54」(JST)

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An autoreceptor is a receptor located in presynaptic nerve cell membranes which serves as a part of a negative feedback loop in signal transduction. It is sensitive only to those neurotransmitters or hormones that are released by the neuron in whose membrane the autoreceptor sits. Similarly, a heteroreceptor is one that is sensitive to neurotransmitters and hormones that are not released by the cell in whose membrane it is embedded. Thus a given receptor can act as either an autoreceptor or a heteroreceptor, depending upon the type of transmitter released by the cell in whose membrane it is embedded.

Autoreceptors may be located in any part of the cell membrane: in the dendrites, the cell body, the axon, or the axon terminals.

Canonically, a presynaptic neuron releases neurotransmitter across a synaptic cleft to be detected by the receptors on a postsynaptic neuron. Autoreceptors on the presynaptic neuron will also detect this neurotransmitter and often function to control internal cell processes, typically inhibiting further release or synthesis of the neurotransmitter. Thus, release of neurotransmitter is regulated by negative feedback. Autoreceptors are usually G protein-coupled receptors (rather than transmitter-gated ion channels) and act via a second messenger.

Examples

As an example, norepinephrine released from sympathetic neurons may interact with the alpha-2A and alpha-2C adrenoreceptors to inhibit further release of norepinephrine. Similarly, acetylcholine released from parasympathetic neurons may interact with M₂ and M₄ receptors to inhibit further release of acetylcholine. An atypical example is given by the β-adrenergic autoreceptor in the sympathetic peripheral nervous system, which acts to increase transmitter release.

The D2sh autoreceptor interacts with the trace amine-assorted receptor 1 (TAAR1), a recently discovered GPCR, to regulate monoaminergic systems in the brain. Active TAAR1 opposes the autoreceptor's activity by inactivating the dopamine transporter (DAT). In their review of TAAR1 in monoaminergic systems, Xie and Miller proposed this schematic: synaptic dopamine binds to the dopamine autoreceptor, which activates the DAT. Dopamine enters the presynaptic cells and binds to TAAR1, which increases adenylyl cyclase activity. This eventually allows for the translation of trace amines in the cytoplasm and activation of cyclic nucleotide-gated ion channels, which further activate TAAR1 and dump dopamine into the synapse. Through a series of phosphorylation events related to PKA and PKC, active TAAR1 inactivates DAT, preventing uptake of dopamine from the synapse. The presence of two presynaptic receptors with opposite abilities to regulate monoamine transporter function allows for regulation of the monoaminergic system.

Autoreceptor activity may also decrease paired-pulse facilitation (PPF). A feedback cell is activated by the (partially) depolarized post-synaptic neuron. The feedback cell releases a neurotransmitter to which the autoreceptor of the presynaptic neuron is receptive. The autoreceptor causes the inhibition of calcium channels (slowing calcium ion influx) and the opening of potassium channels (increasing potassium ion efflux) in the presynaptic membrane. These changes in ion concentration effectively diminish the amount of the original neurotransmitter released by the presynaptic terminal into the synaptic cleft. This causes a final depression on the activity of the postsynaptic neuron. Thus the feedback cycle is complete.

This diagram shows pre-synaptic neuron (left) releasing a neurotransmitter, noradrenaline (norepinephrine), into the synaptic cleft. The transmitter acts on the receptors of the post-synaptic neuron (right), but also on autoreceptors of the pre-synaptic neuron. Activation of these autoreceptors typically inhibits further release of the neurotransmitter.

Amphetamine, trace amines, and dopamine can activate TAAR1 in dopamine neurons,but only dopamine activates D2sh. These receptors have opposite effects on protein kinase signaling. This results in opposite effects on DAT phosporylation, and consequently, on reuptake as well.

References

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Japanese Journal

• Brain Science(94)セロトニン自己受容体とヘテロ受容体の新展開

• 田中 謙二
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Related Links

• autoreceptor - definition of autoreceptor by Medical dictionary

autoreceptor A neurotransmitter receptor located in the presynaptic terminal of the same neuron that produces the neurotransmitter. Autoreceptors have a higher affinity for the neurotransmitter than does the postsynaptic receptor, and ...

• What does autoreceptor mean?

Definition of autoreceptor in the Definitions.net dictionary. Meaning of autoreceptor. What does autoreceptor mean? Information and translations of autoreceptor in the most comprehensive dictionary definitions resource on the web.

Related Pictures

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★リンクテーブル★

リンク元	「ドパミン受容体」「D2受容体」

「ドパミン受容体」

　　[★]

英

dopamine receptor DA-R

同

ドーパミン受容体

関

ドパミン、ドーパミン作動性ニューロン、受容体、カテコールアミン受容体

[show details]

ドーパミン受容体 : 約 37,500 件
ドパミン受容体 : 約 21,600 件

• GOO.249
• ７回膜貫通型Gタンパク共役型受容体
• D₁受容体

G_s：アデニル酸シクラーゼ活性化→[cAMP]_i↑

低用量での血管拡張はこの受容体を介して起こる

大脳基底核の神経回路では直接路にかかわる(SP.377)。

• D₂受容体

G_i：アデニル酸シクラーゼ抑制→[cAMP]_i↓、K⁺チャネル活性化、Ca²⁺チャネル抑制

中枢神経系に存在

シナプス後ニューロン、ドーパミン作動性ニューロンの細胞体・樹状突起・軸索・終末部に存在し、興奮性の調節に関わる

autoreceptor

大脳基底核の神経回路では間接路にかかわる(SP.377)。

作動薬(アゴニスト)

• タンドスピロン tandospirone

拮抗薬(アンタゴニスト)

• クロルプロマジン chlorpromazine

「D2受容体」

　　[★]

英

D2 receptor

関

ドパミン、ドパミン受容体、受容体

• リガンド：ドパミン
• 受容体の型：7回膜貫通型G蛋白質共役受容体
• サブユニットの型：G_i：アデニル酸シクラーゼ抑制→[cAMP]_i↓、K⁺チャネル活性化、Ca²⁺チャネル抑制
• 局在：中枢神経系に存在
• 機能：

• シナプス後ニューロン、ドーパミン作動性ニューロンの細胞体・樹状突起・軸索・終末部に存在し、興奮性の調節に関わる
• autoreceptor
• 大脳基底核の神経回路では間接路にかかわる(SP.377)。