CNS Neurotransmitter Systems: Monoamines

Vocabulary-style flashcards covering CNS monoamine neurotransmitters, including dopamine, noradrenaline, serotonin, and acetylcholine, their synthesis, receptors, physiological roles, and associated clinical conditions.

Monoamine Neurotransmitters

A class of neurotransmitters derived from aromatic amino acids like tyrosine (noradrenaline) and tryptophan (serotonin); within the CNS, these include Acetylcholine, Noradrenaline, Serotonin, and Dopamine.

Nucleus

A collection of neurons that expresses a common chemical, such as dopaminergic nuclei where neurons commonly express dopamine (DA).

Major Dopamine (DA) nuclei

The Substantia nigra, Ventral tegmental area, and Hypothalamus.

Dopamine (DA) receptors

Five specific receptors ($D_1$, $D_2$, $D_3$, $D_4$, and $D_5$), all of which are metabotropic and can cause excitation or inhibition depending on the G-proteins they are coupled to.

Roles of Dopamine in brain function

Motor coordination, motivation, reward seeking, cognition, and nausea and vomiting.

Tyrosine hydroxylase

The enzyme used in the synthesis of dopamine and noradrenaline (NA) from the precursor tyrosine.

Vesicular monoamine transporter (VMAT)

The transporter responsible for packing produced dopamine, noradrenaline, serotonin, and acetylcholine into vesicles for release.

G-protein S coupled DA receptors

Postsynaptic $D_1$ and $D_5$ receptors that dopamine binds to after release.

G-protein I coupled DA receptors

$D_2$, $D_3$, and $D_4$ receptors; note that $D_2$ and $D_3$ can be expressed on both the presynapse and postsynapse.

Locus coeruleus

The major nucleus for Noradrenaline (NA).

Noradrenergic receptors

Alpha $1$, Alpha $2$, and Beta $1$, $2$, and $3$ receptors; all are metabotropic and can be either pre/postsynaptic.

Roles of Noradrenaline (NA) in brain function

Arousal, memory and cognition, and stress response.

Alpha $2$ receptor (presynaptic)

A receptor located on the presynapse that, when bound by Noradrenaline, can decrease the further release of NA.

Raphe nuclei

A collection of nuclei in the midbrain and pons that serve as the major source of Serotonin (5HT).

Serotonergic receptors (5HT)

Seven sub-classes ($5HT_1$, $5HT_2$, $5HT_3$, etc.); all are metabotropic except for $5HT_3$, which is ionotropic.

Tryptophan hydroxylase

The enzyme used in the synthesis of Serotonin ($5HT$) from the precursor tryptophan.

MAO and COMT

Enzymes responsible for the oxidation/degradation of monoamine neurotransmitters like dopamine and noradrenaline after they have expressed their effects.

Major Acetylcholine (Ach) nuclei

Nucleus basal, the medial septal nucleus and diagonal band, and the pedunculopontine nucleus in the brainstem.

Nicotinic receptors

A class of ionotropic acetylcholine receptors consist of $17$ subunits.

Muscarinic receptors

A class of metabotropic acetylcholine receptors with $5$ subtypes ($M_1$-$M_5$).

Choline acetyltransferase

The enzyme used in the synthesis of Acetylcholine (Ach) from the precursor choline.

AChE (Acetylcholinesterase)

The enzyme used to degrade Acetylcholine (Ach) at the postsynaptic membrane.

Ritalin

A drug used to treat ADHD by increasing noradrenergic transmission to improve arousal/attention.

Tricyclic antidepressants

Drugs that treat depression by inhibiting the uptake of noradrenaline and $5HT$ (serotonin).

Haloperidol

A dopamine antagonist used as an antipsychotic to treat Schizophrenia, which is caused by elevated dopamine function.

L-DOPA and Apomorphine

Treatment for Parkinson's disease; L-DOPA is a dopamine precursor and Apomorphine is a dopamine agonist, used to address the degeneration of nigrostriatal dopamine neurons.

Mesolimbic dopamine system

The system whose activation is linked to addiction symptoms and the effects of many drugs of abuse that increase dopamine.