Neurotransmitters: Types, Functions, and Receptor Mechanisms

Neurotransmitters

Chemical messengers that allow one neuron to influence actions of another

Endogenous

A substance produced inside the body; 'natural'

Exogenous

A substance produced outside the body; 'synthetic'

Agonists

Ligands that mimic or potentiate effects of a neurotransmitter

Antagonists

Ligands that block or reduce the effects of a neurotransmitter

Ionotropic receptors

Rapid, short-term effects caused by change in distribution of ions

Metabotropic receptors

Slower, long-term effects caused by second messengers

Neurotransmitter production

Nutrients absorbed from food enter brain through blood brain barrier and are converted into neurotransmitters

Reuptake

Protein transporters on presynaptic cell pull neurotransmitters back in

Autoreceptors

Protein transporter that provides presynaptic cell feedback on how much neurotransmitter is being released

Degradation

Enzymes rapidly break down neurotransmitter

Synaptic vesicles

Tiny storage pockets in presynaptic axon terminals

Glutamate

Primary excitatory neurotransmitter (makes other neurons fire by producing EPSPs)

GABA (Gamma-aminobutyric acid)

Primary inhibitory neurotransmitter (prevents other neurons from firing by producing IPSPs)

Acetylcholine (ACh)

Muscle movement, learning and memory

Dopamine (DA)

Coordinated movement, motivation, reward learning, executive function

Norepinephrine (NE)

Stress response, alertness, cognition

Serotonin (5-HT)

Many functions; sleep, mood, sexual behavior, appetite, anxiety, vision

Cocaine

Blocks DA transporter from clearing leftover DA from synapse

Parkinson's Disease

DA-producing cells in substantia nigra die

SSRIs

Common target for antidepressants affecting serotonin