Neurotransmitters and MAOIs Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following neurotransmitters are considered catecholamines?

Serotonin

Epinephrine (correct)

Dopamine (correct)

GABA

What is the initial step in the biosynthetic pathway of catecholamines?

Production of dopamine from L-dopa

Conversion of tyrosine to norepinephrine

Conversion of L-phenylalanine to L-tyrosine (correct)

Formation of epinephrine from dopamine

What severe condition can be triggered by consuming aged cheese while on MAOIs?

Heartworm infection

Diabetes

Hypertensive crises (correct)

Anemia

What symptoms are typically experienced 1-2 hours after consuming tyramine-rich foods while on MAOIs?

Severe headaches and palpitations Signup and view all the answers

What role does the enzyme tyrosine hydroxylase play in dopamine synthesis?

Converts tyrosine into L-dopa Signup and view all the answers

Which of the following complications is NOT associated with hypertensive crises induced by MAOIs?

Diabetic ketoacidosis Signup and view all the answers

Where are the dopaminergic nuclei primarily located in the brain?

Substantia nigra and ventral tegmental area Signup and view all the answers

The 'cheese effect' primarily refers to the reaction caused by which substance in cheese?

Tyramine Signup and view all the answers

What can result from D2 receptor inhibition in the striatum?

Symptoms resembling Parkinson's disease Signup and view all the answers

Which medication has a lower tendency to produce side effects associated with D2 receptor inhibition?

Clozapine Signup and view all the answers

How is noradrenaline synthesized from dopamine?

By adding a hydroxyl group Signup and view all the answers

What role does noradrenaline play in the body?

Regulating attention and impulsivity Signup and view all the answers

Where are the majority of noradrenaline neurons located?

Locus coeruleus Signup and view all the answers

What process converts noradrenaline into adrenaline?

Addition of a methyl group Signup and view all the answers

Which enzyme catalyzes the reaction that transforms dopamine into noradrenaline?

Dopamine β-hydroxylase (DBH) Signup and view all the answers

What are the mechanisms for terminating the actions of dopamine, noradrenaline, and adrenaline?

Reuptake and enzymatic degradation Signup and view all the answers

What leads to tolerance and dependence in opiate users?

Adaptations in LC neurons Signup and view all the answers

What role does COMT play in neurotransmitter regulation?

It breaks down dopamine and catecholamines. Signup and view all the answers

What risk is associated with consuming tyramine while on monoamine oxidase inhibitors (MAOIs)?

Hypertensive crisis Signup and view all the answers

What consequence did MPTP contamination in meperidine have on individuals?

It led to Parkinsonian symptoms. Signup and view all the answers

What does tyramine stimulate the release of, contributing to a hypertensive crisis?

Norepinephrine and adrenaline Signup and view all the answers

How do DA receptors affect adenylyl cyclase activity?

D1-like receptors stimulate its activity, while D2-like receptors inhibit it. Signup and view all the answers

Which food types are high in tyramine and should be avoided by those on MAOIs?

Aged cheeses and cured meats Signup and view all the answers

What is the primary effect of selective MAO-B inhibitor selegiline?

Helps mitigate oxidative stress in Parkinson's disease. Signup and view all the answers

Which symptoms are indicative of a hypertensive crisis?

Headache and stiff neck Signup and view all the answers

What type of effect do D1-like receptors typically have?

Excitatory effects stimulating adenylyl cyclase. Signup and view all the answers

Which treatments are commonly used for ADHD?

Methylphenidate and amphetamines. Signup and view all the answers

Which aspect of dopamine's role is still not fully understood?

How it contributes to psychotic symptoms. Signup and view all the answers

What is the mechanism by which antipsychotic drugs reduce symptoms of psychosis?

By blocking D2 receptors in subcortical structures. Signup and view all the answers

What is the first step in the production of noradrenaline?

Tyrosine is converted to Dopa. Signup and view all the answers

Which enzyme catalyzes the conversion of dopamine to noradrenaline?

Dopamine-β-hydroxylase (DBH) Signup and view all the answers

How is the action of noradrenaline terminated in the presynaptic neuron?

Through reuptake by the norepinephrine transporter (NAT) Signup and view all the answers

What enzyme is NOT involved in the breakdown of noradrenaline?

Dopamine-β-hydroxylase (DBH) Signup and view all the answers

Which type of adrenoreceptor is generally inhibitory?

α2 auto receptor Signup and view all the answers

Which enzyme metabolizes all catecholamines, including noradrenaline and adrenaline?

Monoamine Oxidase Signup and view all the answers

What role do COMT inhibitors play in catecholamine action?

They increase levels of catecholamines in synapses. Signup and view all the answers

Which of the following statements about adrenoreceptors is correct?

Adrenoreceptors are all metabotropic. Signup and view all the answers

What is the primary function of auto receptors in the nervous system?

Inhibit activity Signup and view all the answers

How do α-adrenergic receptors affect noradrenergic cell bodies upon activation?

Decrease firing rate Signup and view all the answers

What effect does the locus coeruleus have on memory during situations of strong negative emotions?

Enhances memory for danger-related stimuli Signup and view all the answers

What consequences arise from the activation of presynaptic α-ARs in the synaptic terminal?

Inhibition of further NA synthesis Signup and view all the answers

Which system does the adrenergic function primarily target?

Autonomic nervous system Signup and view all the answers

Which of the following is a potential application of β-adrenergic receptor antagonists?

Reducing intensity of traumatic memories in PTSD Signup and view all the answers

Which of the following drugs is known to increase synaptic noradrenaline and is used to treat ADHD?

Desipramine Signup and view all the answers

In what scenarios does increased firing of the locus coeruleus potentially lead to heightened anxiety?

In response to perceived threats Signup and view all the answers

Study Notes

Catecholamines

Catecholamines are amine neurotransmitters made from tyrosine.
They include dopamine, norepinephrine, and epinephrine.

Case Study: "Cheese Effect"

A British pharmacist observed wife's headaches after eating cheese while taking MAOIs.
Aged cheese contains high tyramine levels, triggering hypertensive crises in MAOI users.
This was reported in 1962 (Dally & Taylor).
Cheese (cooked or raw) caused blood pressure spikes from 160/90 to 220/115 mmHg.

Symptoms and Complications

Symptoms include severe headaches, heart pounding, and palpitations.
Time between eating and symptoms: 1-2 hours.
Potential complications include subarachnoid hemorrhage, hemiplegia, intracranial hemorrhage, cardiac arrhythmias, cardiac failure, pulmonary edema, and death.

Catecholamine Synthesis from Tyrosine

Catecholamines are synthesized from L-phenylalanine, which is converted to L-tyrosine.
Catecholamines contain a catechol group and an amine group.
Dopamine synthesis is a two-step process:
- Tyrosine is actively transported into the brain.
- Tyrosine hydroxylase converts tyrosine to L-dopa.
- Dopa decarboxylase converts L-dopa to dopamine.

Dopaminergic Nuclei Location

Dopamine neurons are located in the substantia nigra and ventral tegmental area (VTA).
Substantia nigra neurons form the nigrostriatal pathway, crucial for motor control.
VTA neurons form the mesocorticolimbic pathway, involved in reward, reinforcement, and behavior.
Parkinson's disease is associated with loss of dopamine neurons in the substantia nigra.

Tyrosine Hydroxylase (TH)

TH is the rate-limiting enzyme in catecholamine synthesis.
Tyrosine transport across the blood-brain barrier is active transport.

Regulation of Tyrosine Hydroxylase (TH) Activity

TH activity increases with catecholamine release.
Stimuli such as chronic stress, caffeine, nicotine, or morphine upregulate TH.
Stimuli such as antidepressants downregulate TH.
L-dopa for Parkinson's disease treatment: Increased dopamine synthesis achieved by peripheral L-dopa administration, bypassing TH step.

Dopamine Termination

Dopamine is reuptaken into the terminal via the Dopamine Transporter (DAT).

Enzymatic Degradation

Dopamine is broken down by Monoamine Oxidase (MAO) and Catechol-O-Methyltransferase (COMT).
MAO exists in intracellular and extracellular forms, and exists as two isoforms MAO-A and MAO-B.
MAO-A is found in dopamine and norepinephrine neurons.
MAO-B is present in serotonin neurons.

MAO Inhibitors (MAOIs)

MAOIs are used to treat Parkinson's disease.
MPTP by-product of illicit drug synthesis causes PD.
Selegiline (deprenyl) is a selective MAO-B inhibitor.

Dopamine Receptors

Dopamine receptors (D1-D5) have both inhibitory and excitatory effects, depending on the receptor subtype.
D1-like receptors (D1 and D5) typically stimulate adenylyl cyclase (AC) activity.
D2-like receptors (D2, D3, and D4) typically inhibit adenylyl cyclase (AC) activity.

Dopamine Receptors in Diseases

Dopamine plays a role in cognitive control of behavior and working memory.
Psychostimulants increase dopamine levels by blocking the dopamine transporter (DAT).
Antipsychotic drugs block D2 receptors to reduce delusions and hallucinations associated with psychosis.
Parkinson's disease is managed with D2 agonists such as bromocriptine.

Noradrenaline from Dopamine

Noradrenaline is synthesized from dopamine by adding a hydroxyl group, catalyzed by dopamine β-hydroxylase (DBH), to dopamine.

Noradrenaline Location and Function

Noradrenaline neurons are in the locus coeruleus.
Noradrenaline plays a key role in attention and impulsivity; central to autonomic functions (heart rate, blood pressure).

Noradrenaline Termination

Noradrenaline is terminated by reuptake via transporters and enzymatic degradation (MAO and COMT).

Adrenaline from Noradrenaline

Adrenaline is synthesized from noradrenaline by the addition of a methyl group, catalyzed by phenylethanolamine N-methyltransferase (PNMT).

Adrenaline Mechanisms and Termination

Adrenaline mechanisms and termination are similar to dopamine and noradrenaline.

Auto Receptors

Autoreceptors on noradrenergic cells inhibit activity when stimulated.
This creates a negative feedback loop regulating signalling and reducing firing rates.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on neurotransmitters, especially catecholamines, and their biosynthesis pathways. Understand the implications of monoamine oxidase inhibitors (MAOIs) and related conditions like the 'cheese effect'. This quiz covers key concepts in neurochemistry and pharmacology relevant to mental health and medication safety.