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Serotonin is a monoamine that exists in virtually all smooth muscle and peripheral tissues, such as platelets, and has a profound effect on these tissues. It can cause smooth muscle contraction by acting on D-serotonin receptors, and S2-serotonergic receptors. Serotonin's effect on vascular constriction is defined by the balance between its contractile and relaxatory actions. For example, serotonin causes contraction of the smooth muscles of the vas deferens and of a strip of the rat stomach, and in human hand veins.
| Characteristics | Values |
|---|---|
| Serotonin causes contraction of smooth muscles | By acting on D-serotonin receptors |
| By activating S2-serotonergic receptors | |
| By acting on 5-HT1, 5-HT2 and rat stomach fundus 5-HT receptors | |
| By acting on 5-hydroxytryptamine-induced receptors | |
| Serotonin can cause relaxation | Through activation of serotonergic receptors |
| Through an inhibitory effect on adrenergic neurotransmission | |
| Serotonin's contractile effects can be enhanced by | Hypoxia or moderate cooling |
| Loss of relaxatory ability | |
| Hypersensitivity of smooth muscle cells | |
| Local physical or humoral factors | |
| Serotonin possesses clinically important actions | On organs outside the central nervous system |
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What You'll Learn
- Serotonin causes contraction of smooth muscles in the rat stomach and vas deferens
- Serotonin's effect on vascular constriction is defined by a balance of actions
- Serotonin affects receptors in the cerebral arteries
- Serotonin can cause relaxation through activation of serotonergic receptors
- Serotonin affects tissues outside the central nervous system
Serotonin causes contraction of smooth muscles in the rat stomach and vas deferens
Serotonin is a monoamine that can cause smooth muscle contraction in most blood vessels. Serotonin causes contraction of the smooth muscles of the vas deferens and a strip of the stomach in rats. This action is mediated by D-serotonin receptors, with only a small part (about 10-14%) of its contractile effect due to the liberation of endogenous catecholamines.
The effect of serotonin on vascular constriction is defined by the balance between its various actions. Serotonin can also cause relaxation through the activation of serotonergic receptors, which differ from the S2-serotonergic receptor and are located on endothelial cells. In certain blood vessels, the contractile effects can be enhanced by hypoxia or moderate cooling. At low concentrations, serotonin amplifies the vasoconstrictor responses to other vasoactive substances.
The presence of serotonin in virtually all smooth muscles and other peripheral tissues, such as platelets, suggests that it possesses clinically important actions on organs outside the central nervous system. For example, serotonin can affect immunological tissue components, platelets, cardiovascular, gastrointestinal, respiratory, and genitourinary smooth muscle.
The complex actions of serotonin on blood vessels result from interactions with a variety of specific 5-HT receptors. Recent advances have been made in defining the receptor subtypes involved, including their pharmacology, biochemistry, and molecular biology. This has led to an evolution in the criteria used for classifying and naming these receptors.
In rats, the contractile response to serotonin in the stomach fundus is not mediated by the activation of the 5-hydroxytryptamine1C receptor, according to pharmacological and molecular evidence.
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Serotonin's effect on vascular constriction is defined by a balance of actions
Serotonin is a monoamine that exists in almost all smooth muscles and other peripheral tissues, such as platelets, and has profound effects on these tissues. It can cause the contraction of smooth muscles, such as in the vas deferens and stomach. This contraction is primarily due to the activation of S2-serotonergic receptors. However, serotonin can also cause relaxation through the activation of serotonergic receptors located on endothelial cells and by inhibiting adrenergic neurotransmission.
The constrictor action of serotonin can be attributed to three main mechanisms:
- Direct activation of vascular smooth muscle, often mediated by S2-serotonergic receptors.
- Augmentation of the effects of other endogenous vasoconstrictors like catecholamines, angiotensin II, and prostanoids.
- Release of norepinephrine from adrenergic nerves.
On the other hand, the dilator or relaxatory action of serotonin involves:
- Activation of endothelial cells, leading to the release of endothelium-derived relaxing factors.
- Direct inhibition of vascular smooth muscle.
- Inhibition of adrenergic neurotransmission through S1-serotonergic prejunctional receptors.
- Release of other endogenous mediators.
The net effect of serotonin on vascular constriction or dilation is a balance between these constrictor and dilator actions. Under normal conditions, serotonin may play a modulatory role. However, an exacerbation of the contractile effects due to hypersensitivity of smooth muscle cells, local factors, or a loss of relaxatory ability may lead to abnormal tissue responses and potentially contribute to vasospasm and peripheral vascular diseases.
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Serotonin affects receptors in the cerebral arteries
Serotonin, or 5-hydroxytryptamine (5-HT), is a neurotransmitter that plays a key role in various bodily functions, including mood, sleep, appetite, anxiety, digestion, blood clotting, and sexual desire. It is found in virtually all smooth muscles and peripheral tissues, such as platelets, and can have profound effects on these tissues. For example, serotonin affects immunological tissue components, platelets, cardiovascular, gastrointestinal, respiratory, and genitourinary smooth muscle.
In terms of its effects on cerebral arteries, serotonin can cause vasoconstriction or vasodilation. Vasoconstrictor responses to serotonin released from aggregating platelets may contribute to spasms in cerebral, digital, and coronary vessels. This constrictor action is primarily due to the activation of S2-serotonergic receptors. In most blood vessels, serotonin directly activates vascular smooth muscle through these S2-serotonergic receptors. However, it can also amplify the action of other endogenous vasoconstrictors, such as catecholamines, angiotensin II, and prostanoids. Additionally, serotonin can cause the release of norepinephrine from adrenergic nerves.
On the other hand, serotonin can also induce vasodilation through several mechanisms. It can activate endothelial cells, leading to the release of endothelium-derived relaxing factors. This response is mediated by S1-serotonergic receptors. Serotonin can also directly inhibit vascular smooth muscle, inhibit adrenergic neurotransmission by acting on S1-serotonergic prejunctional receptors, and release other endogenous mediators. The net effect of serotonin on the blood vessel wall depends on the integrity of the endothelium and the degree of activation of the vascular smooth muscle.
The complex actions of serotonin on blood vessels are due to its interaction with multiple subtypes of 5-HT receptors. These receptors are classified based on their pharmacology, biochemistry, and molecular biology. For instance, the 5-HT2 receptor has been implicated in vascular serotonin receptor activity, particularly in the dog hindlimb and rabbit arteries. Additionally, the 5-HT1 receptor has been linked to serotonin-induced contractions in the canine basilar artery.
In summary, serotonin affects receptors in the cerebral arteries by interacting with various subtypes of 5-HT receptors, leading to either vasoconstriction or vasodilation. The net effect depends on the balance between these opposing actions and is influenced by factors such as the integrity of the endothelium and the activation state of the vascular smooth muscle.
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Serotonin can cause relaxation through activation of serotonergic receptors
Serotonin, also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and peripheral tissues. It is involved in mood, cognition, reward, learning, memory, and physiological processes such as vomiting and vasoconstriction.
While serotonin is often associated with its role in mood and emotion regulation, it also has significant effects on smooth muscle contraction and relaxation. Serotonin exists in virtually all smooth muscles and peripheral tissues, such as platelets, and exerts profound effects on these tissues.
The complex actions of serotonin on blood vessels result from interactions with various specific 5-HT receptors. For example, the activation of 5-HT2 receptors, particularly in vascular smooth muscle, has been implicated in contraction. However, serotonin can also cause relaxation through activation of serotonergic receptors different from the S2-serotonergic receptor and located on endothelial cells or through an inhibitory effect on adrenergic neurotransmission.
In certain blood vessels, serotonin's contractile effects can be enhanced by factors such as hypoxia or moderate cooling. At low concentrations, serotonin amplifies the vasoconstrictor responses to other vasoactive substances. Ultimately, the effect of serotonin on vascular constriction is defined by the balance between these different actions and interactions with specific receptors.
Additionally, serotonin released by platelets in the blood during clotting promotes vasoconstriction and platelet aggregation, contributing to wound healing. This process involves the narrowing of the tiniest blood vessels (arterioles) to slow blood flow and facilitate clot formation.
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Serotonin affects tissues outside the central nervous system
Serotonin causes contraction of the vascular smooth muscle cells in most blood vessels studied in vitro. This contraction is mainly due to the activation of S2-serotonergic receptors. However, serotonin can also cause relaxation through the activation of serotonergic receptors, which are different from the S2-serotonergic receptor and located on endothelial cells. In certain blood vessels, the contractile effects can be enhanced by hypoxia or moderate cooling. At low concentrations, serotonin amplifies the vasoconstrictor responses to other vasoactive substances.
Serotonin has been found to cause the contraction of the smooth muscles of the deferent duct and of the strip of rat stomach, acting upon the D-serotonin receptors. Only a small portion of its contractile effect (about 10-14%) was caused by the release of endogenous catecholamines. The action of serotonin on the strip of the rat stomach was accompanied by an increase in its entrance into the cells of Ca45 and Na22 isotopes. The concentration turn of the concentration-effect curve of serotonin on the stomach strip was connected with the accumulation of sodium ions in the cells.
The complex actions of 5-hydroxytryptamine (5-HT) on blood vessels result from interactions with a variety of specific 5-HT receptors. There have been dramatic advances in defining the receptor subtypes involved in terms of their pharmacology, biochemistry, and molecular biology.
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Frequently asked questions
Serotonin, or 5-hydroxytryptamine (5-HT), is a monoamine that exists in virtually all smooth muscle and other peripheral tissues, such as platelets.
Serotonin causes contraction of smooth muscles by acting on D-serotonin receptors. This contraction is mainly due to the activation of S2-serotonergic receptors.
In certain blood vessels, the contractile effects of serotonin can be enhanced by hypoxia or moderate cooling.
The effect of serotonin on vascular constriction is defined by the balance between its contractile and relaxatory actions. Under normal conditions, serotonin may play a modulatory role, but exacerbation of contractile effects can lead to abnormal tissue responses.
