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An autoreceptor is a receptor located on presynaptic nerve cell terminals and serves as a part of a 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.

Canonically, a presynaptic neuron releases the neurotransmitter across a synaptic cleft to be detected by the receptors on a postsynaptic neuron. An autoreceptor will detect this neurotransmitter from its position on the presynaptic membrane. For example, presynaptic NMDA receptors are sensitive to glutamate released from presynaptic vesicles.

Autoreceptors usually do not generate changes in membrane potential. Instead, they often function to control internal cell processes, including the synthesis and release of neurotransmitters.

Autoreceptors are located on or close to those axon terminals of a neuron through which the neuron's own transmitter can modify transmitter synthesis and release. For example, norepinephrine released from sympathetic neurons may interact with alpha-2A and alpha-2C receptors to inhibit neurally released norepinephrine. Similarly, acetylcholine released from parasympathetic neurons may interact with muscarinic-2 and muscarinic-4 receptors to inhibit neurally released acetylcholine.

An example of an autoreceptor's functioning occurs in the depression of PPF (post-synaptic potential facilitation), in which a feedback cell is activated by the post-synaptic neuron when this cell is exitated, to excite a neurotransmitter to which the autoreceptor of the presynaptic neuron is receptive, and the autoreceptor causes the inhibition of calcium channels and the opening of K+ channels in the presynaptic. This in summary causes an inhibition on the exocitaton of the canonical neurotransmitter released by the presynaptic neuron, which causes a final depression on the activity of the postsynaptic neuron.

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