Neurotransmitter systems Flashcards
What are the three main categories of classical neurotransmitters? What neurotransmitters are in each category?
amino acids - glutamate, GABA (gamma aminobutyric acid), glycine
monoamines - catecholamines (dopamine, epinephrine, norepinephrine), indolamines (serotonin and melatonin), acetylcholine, histamine
peptides
nucleosides
lipid-derived NTs - anandamine, 2AG (arachidonic acid derivatives)
Gas NTs - nitric oxide
What are the two main receptors that neurotransmitters act upon?
ligand-gated channels (ionotropic receptors)
GPCR (metabotropic receptors)
What ions flow through ligand-gated channels? What neurotransmitters lead to these types of currents?
Na+ - excitatory postsynaptic current; glutamate, acetylcholine, serotonin, nucleosides
Cl- - inhibitory postsynaptic current; GABA and glycine
What are the three main types of opioid peptides? What types of brain functions do these peptides promote?
Enkephalins - positive mood, analgesia, sedation
endorphins - positive mood, analgesia, sedation
dynorphins - negative mood, analgesia and sedation
What area in the brain produces orexin? What brain functions does orexin promote? What happens when a person lacks orexin producing neurons (from autoimmune destruction)?
Orexin is produces in the lateral hypothalamus and promotes awakeness.
A lack of orexin producing neurons will result in narcolepsy
What are the peptide neurotransmitters?
orexin
opioid peptides (enkephalins, endorphins, dynorphins)
hypothalamic inhibitory and releasing factors (CRF, TRF, somatostatin, GnRH)
Feeding/”gut brain” NTs (neuropeptide Y, vasoactive intestinal peptide, cholecystokinin)
What types of receptors does glutamate activate?
Ligand-gated: AMPA, NMDA, kainate
GPCR: mGluRs (metabotropic glutamate receptors)
What happens to glutamate after it is released from the presynaptic vesicles? GABA?
Glutamate
1) direct reuptake into presynaptic neuron by transporters
2) (glutamate recycling) reuptake into neighboring astrocytes that convert glutamate to glutamine via glutamine synthase. The astrocyte pumps glutamine into the presynaptic neuron where is is converted back into glutamate via glutaminase
GABA
direct reuptake into presynaptic neuron by transporters
What are the major excitatory neurotransmitters? inhibitory neurotransmitters?
excitatory: glutamate
inhibitory: GABA (brain and spinal cord) and glycine (spinal cord)
What types of receptors does GABA activate?
ligand-gated: GABA-A
GPCR: GABA-B (autoreceptors) and GABA-C
How is GABA synthesized? Degraded?
synthesis: glutamate -> GABA via GAD, glutamic acid decarboxylase
Degradation via GABA transaminase
What drugs act on GABA receptors?
Benzodiazapenes and barbiturates act on GABA-A and promote it’s function
anticonvulsants block GABA reuptake into presynaptic neuron and increase GABA synthesis
How is glutamate synthesized?
synthesis
1) glutamine -> glutamate via glutaminase
2) aspartate + alpha-ketoglutarate -> oxaloacetate + glutamate via aspartate transaminase
3) alanine + alpha-ketoglutarate -> pyruvate + glutamate via alanine transaminase
What role does glycine have on glutamate receptors?
NMDA receptors require co-activation by glycine in order for glutamate to stimulate the post-synaptic neuron
What is the precursor molecule for the indolamines? What is their synthetic pathway?
tryptophan -> 5-Hydroxytryptophan -> 5-hydroxytryptamine (5HT/serotonin) -> -> melatonin
