PCOL 3-2 Monoamines

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Questions and Answers

Which neurotransmitters are classified as a catecholamine?

Melatonin, Serotonin

Melatonin, Serotonin, Dopamine

Serotonin, Dopamine

Noradrenalin, Adrenalin, Dopamine (correct)

What is the defining structural feature of monoamines?

Contain 2 aromatic rings connected to an amino group by a 3-carbon chain

Contain 1 aromatic ring connected to an amino group by a 2-carbon chain (correct)

Contain 1 aromatic ring connected to a carboxyl group by a 3-carbon chain

Contain 1 aliphatic ring connected to an amino group by a 2-carbon chain

Which cognitive processes are regulated by monoamines?

Long-term memory and logical reasoning

Visual perception and decision making

Emotional and arousal (correct)

Language processing and motor skills

Which enzyme is mainly involved in the synthesis of monoamine neurotransmitters?

Aromatic L-amino acid decarboxylase Signup and view all the answers

Where is the characteristic anatomical distribution of the synthesis of monoamine neurotransmitters?

Limited to a few subcortical or brainstem regions Signup and view all the answers

Which type of receptors do monoamine neurotransmitters mainly activate?

G protein-coupled receptors Signup and view all the answers

Which enzyme is primarily responsible for the synthesis of monoamine neurotransmitters?

Aromatic amino acid decarboxylase Signup and view all the answers

What is the characteristic anatomical distribution of the synthesis of monoamine neurotransmitters?

Limited to a few subcortical or brainstem regions projecting to multiple cortical and limbic target regions Signup and view all the answers

What is the main type of receptors activated by monoamine neurotransmitters?

G protein-coupled receptors (GPCRs) Signup and view all the answers

Which enzyme is responsible for the rate-limiting step in the synthesis of catecholamines?

Tyrosine hydroxylase Signup and view all the answers

Which enzyme catalyzes the conversion of L-tryptophan to 5-HPT in the synthesis of indoleamines?

Tryptophan hydroxylase Signup and view all the answers

Which transporter is responsible for the storage of monoamine neurotransmitters into vesicles?

VMAT Signup and view all the answers

What is the primary function of L-DOPA in the brain?

Increase DA synthesis in substantia nigra Signup and view all the answers

Which drug is known to compete with endogenous monoamines for vesicular storage?

Amphetamine Signup and view all the answers

Which neurotransmitter is primarily targeted in substance abuse disorders, Parkinson’s, and schizophrenia?

Dopamine (DA) Signup and view all the answers

What is the therapeutic use of 5-HTP?

Treat depression, anxiety, insomnia Signup and view all the answers

Which transporter is responsible for the reuptake of serotonin?

SERT Signup and view all the answers

Which enzyme is specific for the degradation of dopamine only?

MAO-B Signup and view all the answers

Which drug competes with endogenous ligands at dopamine, norepinephrine, and serotonin transporters?

Amphetamines Signup and view all the answers

Which class of drugs is used clinically in depression and Parkinson’s disease?

MAOIs Signup and view all the answers

Which CNS function/disease is NOT affected by monoamines, according to the text?

Memory Signup and view all the answers

Which neurotransmitter's degradation is not considered a good target due to its association with addiction?

Dopamine Signup and view all the answers

Which drug disrupts the storage of noradrenaline in the vesicular monoamine transporter by disrupting the H+ gradient?

Reserpine Signup and view all the answers

What is the primary effect of amphetamines on vesicular monoamine storage and release?

Disrupt vesicular monoamine storage by competing for VMAT Signup and view all the answers

Where are large amounts of noradrenaline and 5-HT released from in the brain?

In projection areas of varicosities Signup and view all the answers

What effect does cocaine have on dopamine action in the synapse?

Prolongs dopamine action in the synapse by blocking dopamine transporter Signup and view all the answers

What is the primary mode of active transport for monoamine reuptake into neurons?

High affinity Na+-dependent membrane transporter protein Signup and view all the answers

Which neurotransmitter is primarily associated with the regulation of feeding and sexual behavior?

Serotonin Signup and view all the answers

Which neurotransmitter is specifically linked to the centrally-mediated control of autonomic function?

Noradrenaline Signup and view all the answers

Which neurotransmitter is primarily responsible for the regulation of temperature and blood pressure?

Serotonin Signup and view all the answers

Study Notes

Catecholamines

Catecholamines include dopamine, norepinephrine, and epinephrine.
These neurotransmitters share the catechol structure, characterized by a benzene ring with two hydroxyl groups.

Monoamines

The defining structural feature of monoamines is the presence of an amine group (-NH2) attached to an aromatic ring.
Monoamines regulate various cognitive processes, such as mood, arousal, memory, and learning.

Synthesis of Monoamines

The main enzyme involved in synthesizing monoamine neurotransmitters is aromatic L-amino acid decarboxylase.
The synthesis of monoamine neurotransmitters primarily occurs in the brainstem and specific regions of the central nervous system.

Receptors and Transport

Monoamine neurotransmitters predominantly activate G protein-coupled receptors (GPCRs).
The rate-limiting step in the synthesis of catecholamines is catalyzed by the enzyme tyrosine hydroxylase.

Indoleamines Synthesis

The enzyme tryptophan hydroxylase catalyzes the conversion of L-tryptophan to 5-hydroxytryptophan (5-HPT) during indoleamine synthesis.

Storage and Function

The vesicular monoamine transporter (VMAT) facilitates the storage of monoamine neurotransmitters into vesicles.
L-DOPA serves as a precursor to dopamine and is primarily used to treat Parkinson’s disease.

Drug Interactions

Reserpine is known to compete with endogenous monoamines for vesicular storage, impairing their function.
Dopamine is primarily targeted in substance abuse disorders, Parkinson’s disease, and schizophrenia.

Therapeutic Uses

5-Hydroxytryptophan (5-HTP) is used therapeutically to increase serotonin levels, benefiting mood and sleep disorders.

Reuptake and Degradation

The serotonin transporter (SERT) is responsible for the reuptake of serotonin into neurons.
Monoamine oxidase (MAO) is specific for the degradation of dopamine, while catechol-O-methyltransferase (COMT) degrades norepinephrine and epinephrine.

Drug Competitions and Classes

Cocaine competes with endogenous ligands at dopamine, norepinephrine, and serotonin transporters, enhancing their synaptic actions.
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs used clinically in treating depression and promoting neurotransmitter balance in Parkinson’s disease.

Impact on CNS Functions

Monoamines are not significantly implicated in the regulation of pain pathways, indicating their selective roles in emotional and cognitive functions.
Endogenous cannabinoids' degradation is less of a therapeutic target due to their strong association with addiction.

Miscellaneous Effects

The drug reserpine disrupts noradrenaline storage by interfering with the vesicular monoamine transporter through the H+ gradient.
Amphetamines enhance vesicular monoamine release, leading to increased neurotransmitter availability in synapses.

Release and Action

Large amounts of noradrenaline and serotonin (5-HT) are released from specific nuclei in the brain, such as the locus coeruleus and raphe nuclei.
Cocaine enhances dopamine action in the synapse by inhibiting its reuptake, increasing its availability.

Transport Mechanisms

The primary mode of active transport for monoamine reuptake into neurons occurs via specific membrane transporters.
Serotonin is primarily associated with the regulation of feeding and sexual behavior.
Norepinephrine is linked to the centrally-mediated control of autonomic functions, including stress responses.
Dopamine plays a crucial role in regulating temperature and blood pressure.

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Description

Test your knowledge on monoamines, a sub-class of neurotransmitters that play a crucial role in regulating cognitive processes such as emotions, arousal, and memory. Learn about their structure and function, as well as their significance in treating psychiatric and neurological disorders.