Autoreceptor
An autoreceptor is a type of receptor located in the membranes of nerve cells. It serves as part of a negative feedback loop in signal transduction. It is only sensitive to the neurotransmitters or hormones released by the neuron on which the autoreceptor sits. Similarly, a heteroreceptor is sensitive to neurotransmitters and hormones that are not released by the cell on which it sits. A given receptor can act as either an autoreceptor or a heteroreceptor, depending upon the type of transmitter released by the cell on which 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 a 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 ...
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Heteroreceptor
A heteroreceptor is a receptor regulating the synthesis and/or the release of mediators other than its own ligand. Heteroreceptors respond to neurotransmitters, neuromodulators, or neurohormones released from adjacent neurons or cells; they are opposite to autoreceptors, which are sensitive only to neurotransmitters or hormones released by the cell in whose wall they are embedded. Examples * Norepinephrine can influence the release of acetylcholine from parasympathetic neurons by acting on α2 adrenergic (α2A, α2B, and α2C) heteroreceptors. * Acetylcholine can influence the release of norepinephrine from sympathetic neurons by acting on muscarinic-2 and muscarinic-4 heteroreceptors. * CB1 negatively modulates the release of GABA and glutamate, playing a crucial role in maintaining a homeostasis between excitatory and inhibitory transmission. * Glutamate released from an excitatory neuron escapes from the synaptic cleft Chemical synapses are biological junctions thro ...
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