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Serotonin Receptors

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5-HT receptor Summary

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Dictionary of Biological Psychology

serotonin receptors

There are multiple receptor subtypes for SEROTONIN. The basic types are identified by numbers (5-HT1 to 5-HT7—5HT stands for 5-HYDROXYTRYPTAMINE, the chemical name for serotonin), these then being further subdivided, indicated by letters. Receptors for serotonin are found throughout the CENTRAL NERVOUS SYSTEM, as well as in the PERIPHERAL NERVOUS SYSTEM and body tissues. They are found at PRESYNAPTIC and POSTSYNAPTIC locations, and can function as AUTORECEPTORS. Many of these classes are however

The prinicpal locations of serotonin receptor subtypes
5-HT1A	HIPPOCAMPUS, SEPTAL NUCLEI, AMYGDALA, FRONTAL CORTEX, ENTORHINAL CORTEX (all postsynaptic); RAPHE NUCLEI (autoreceptors)
5-HT1B	SUBSTANTIA NIGRA, SUBICULUM, GLOBUS PALLIDUS, SUPERIOR COLLICULUS, DORSAL STRIATUM, CENTRAL GRAY
5-HT1D	low levels only in rat brain; more common in human brain where it is found in substantia nigra, globus pallidus, dorsal and VENTRAL STRIATUM
5-ht1E	the distribution of this poorly characterized receptor is unclear
5-HT1F	hippocampus, CEREBRAL CORTEX, raphe nuclei
5-HT2A 2B & 2C	CLAUSTRUM, ventral striatum, OLFACTORY TUBERCLE, PYRIFORM CORTEX, NEOCORTEX. Discrimination between 5-HT2A, 5-HT2B and 5-HT2C inthe central nervous system is unclear; 5-HT2B receptors are found outsidethe central nervous system also (notably in the STOMACH): whether thissubtype is present in brain at all is unclear.
5-HT3	AUTONOMIC NERVOUS SYSTEM; AREA POSTREMA, entorhinal cortex, amygdala, NUCLEUS OF THE SOLITARY TRACT, TRIGEMINAL NERVE nuclei
5-HT4	the distribution of this poorly characterized receptor is unclear
5-ht5A	the distribution of this poorly characterized receptor is unclear
5-ht5B	the distribution of this poorly characterized receptor is unclear
5-ht6	the distribution of this poorly characterized receptor is unclear
5-HT7	the distribution of this poorly characterized receptor is unclear
Note: when lower case is used [5ht] it indicates that although receptors have been cloned (see CLONE), expression of the receptor in whole brain has not yet been achieved.

further subdivided, as is indicated in the table below.

Serotonin receptors are typically coupled to G PROTEIN. The family of 5-HT₃ receptors however are not: activation of this receptor produces direct ION CHANNEL opening (they are LIGAND-GATED ION CHANNELS). Serotonin receptors mediate a variety of electrophysiological effects.

5HT1 receptors affect ADENYLATE CYCLASE activity and produce HYPERPOLARIZATION (that is, inhibition of firing). 5HT₂ receptors affect INOSITOL systems and have depolarizing (see DEPOLARIZATION) effects (that is, they have excitatory effects). 5HT₄ receptors affect adenylate cyclase activity also, but have depolarizing effects. Little is known for certain about the electrophysiological effects of the remaining receptor subtypes.

While it appears that individual subtypes of serotonin receptors rarely act entirely independently of each other, there are a number of drugs that show a degree of selectivity for one or other subtypes. These are catalogued in the table below. Note though that it is unusual to find a drug that has an action exclusively at one type of RECEPTOR: in most cases selectivity for a receptor subtype is relative. The agonists and antagonists listed here, unless otherwise specifically noted, show a degree of selectivity for the receptors indicated, though this selectivity may not necessarily be absolute.

Reference

Feldman R., Meyer J.S. & Quenzer L.F. (1997) Principles of Neuropsychopharmacology, Sinauer Associates: Sunderland MA.

Drugs acting at serotonin receptors
5-HT1A	agonists	8-OH-DPAT, ipsapirone
	antagonists	SDZ 216-525, WAY-100135
5-HT1B	agonists	CP-93,129, sumatripan
	antagonists	SB224289
5-HT1D	agonists	sumatripan
	antagonists	BRL15572
5-htlE	agonists	BRL54443
	antagonists	not available
5-HT1F	agonists	LY334370
	antagonists	not available
5-HT2A	agonists	alpha-methyl 5-hydroxytryptamine
	antagonists	ketanserin, ritanserin
5-HT2B	agonists	alpha-methyl 5-hydroxytryptamine
	antagonists	LY-53857
5-HT2C	agonists	alpha-methyl 5-hydroxytryptamine
	antagonists	mesulergine
5-HT3	agonists	alpha-methyl 5-hydroxytryptamine
	antagonists	tropisetron, ondansetron, granisetron
5-HT4	agonists	alpha-methyl 5-hydroxytryptamine
	antagonists	GR113808
Note: Selective agonists and antagonists for the 5-ht5A, 5-ht5B, 5-ht6 and 5-HT7 receptors are not yet available. When lower case is used [5ht] it indicates that although receptors have been cloned (see clone), expression of the receptor in whole brain has not yet been achieved.