Lecture 6 - Synaptic Transmission II, Neurotransmitters & Receptors Flashcards
what are the 4 classes of small molecule neurotransmitters?
acetylcholine class amino acid class biogenic amine class purine class
what are the 5 classes of peptide neurotransmitters?
hypothalamic hormones neuropeptide Y opioid peptides tachykinins VIP-glucagon family
what are the 3 classes of neurotransmitter types?
small molecule classes
peptide classes
gas class
what is the neurotransmitter of the acetylcholine class?
acetylcholine
where does acetylcholine act on?
acts on the brain, NMJ, autonomic endings, basal ganglia and the GI tract
what are the 3 neurotransmitters of the amino acid class?
glutamate
GABA (Y-aminobutyric acid)
glycine
where do the neurotransmitters of the amino acid class act on?
acts on the brain, spinal cord and the retina
what are the 5 neurotransmitters of the biogenic amine class?
adrenaline noradrenaline dopamine serotonin histamine
where do the neurotransmitters of the biogenic amine class act on?
acts on the brain, spinal cord and sympathetic endings
what are the 2 neurotransmitters of the purine class?
ATP
adenosine
where does the neurotransmitters of the purine class act on?
acts on the brain, autonomic ganglia
where do the neurotransmitters of the peptide class act on?
acts on the brain, spinal cord and pituitary gland
what are the 2 neurotransmitters of the gas class?
nitric oxide
carbon monoxide
where do the neurotransmitters of the gas class act on?
in low does act on the brain, spinal cord and the GI tract
what is the function of metabotropic receptors?
to change metabolic signalling
what is an example of metabotropic receptors?
G-protein coupled receptors
how is the G-protein coupled receptor activated?
binding of a neurotransmitter activates the G-protein
what is the function of an activated G-protein?
to relay intracellular messages to the G-protein subunit or intracellular messengers (effector protein) to modulate ion channels
what is the effect of modulating ion channels in G-protein coupled receptors?
this results in ions channels opening and ions flowing across the membrane
what neurotransmitter classes is a G-protein coupled receptor used for?
used for Ach, biogenic amines, neuropeptides and purine classes
what are ionotropic receptors?
receptors that are themselves an ion channel
where does the neurotransmitter bind on ionotropic receptors?
the neurotransmitter binds to the cell surface receptor because they are lipophilic and cannot cross the cell membrane
what is the effect of a neurotransmitter binding to an ionotropic receptor?
binding opens the ion channels resulting in ions flowing across the membrane
what is a ligand?
something that binds with a biological molecule to form a complex and produces an effect
what is an example of a ligand?
a neurotransmitter
where does the neurotransmitter bind to the ionotropic receptor?
the neurotransmitter binds where the ion channel is an integral part of the receptor
when is the ion channel of an ionotropic receptor closed?
when a neurotransmitter (ligand) is not bound the channel is closed
what are glutamate receptors composed of?
composed of 3 transmembrane domains and 4 subunits
what is the relationship between different subunits and ion channels of glutamate receptors?
different subunits have different properties but can still have the same ion channels
what are the receptor subtypes of glutamate receptors?
NMDA, AMPA and kainate receptors
what are cys-loop receptors composed of?
composed of 4 transmembrane domains and 5 subunits
what are cys-loop receptors?
ligand-gated ion channels that are activated by several different structural neurotransmitters
what are 4 examples of neurotransmitters acting upon cys-loop receptors?
GABA
glycine
serotonin
acetylcholine
what is the relationship between cys-loop receptors and excitation/inhibition?
these receptors can be excitatory or inhibitory based on selectivity
what is the effect of different subunits in cys-loop receptor subtypes?
creates variations in strength, response, timing and duration
what is the most common excitatory synapse in the brain?
glutamate synapse
what is the function of glial cells at glutamatergic synapses?
to actively participate in synaptic transmission
what is glutamate synthesised from?
glutamate is synthesised from glutamine by the enzyme glutaminase
how is glutamate packaged into vesicles?
to be packaged into vesicles glutamine requires energy to be pumped against its concentration gradient into glutamate vesicles by the vGLUT
what is the vGLUT?
vesicular glutamate transporter
how does the exocytosis of glutamate occur?
occurs through glutamate receptors on the cell surface to the postsynaptic cell
how is any extra glutamate cleaned up?
excitatory amino acid transporter (EAAT) cleans up any extra glutamate released and pump it back into the glutamatergic synapse
what are the 3 types of EAAT’s (excitatory amino acid transporters)?
EAAT1
EAAT2
EAAT5
what is glutamate cotransported with?
cotransported with Na+
what is the relationship between metabotropic receptors and the alpha subunit?
the alpha subunit dissociates at the metabotropic receptor
how does the alpha subunit dissociate?
by the activation of ion channels leading to changes in voltage of either depolarisation (more positive) or hyperpolarisation (more negative)
where does alpha subunit dissociation at the metabotropic receptor occur in?
occurs in Na+, K+ and CI- channels in the postsynaptic cell modulated by second messengers
what are second messengers?
small molecules and ions that relay signals received by cell surface receptors to effector proteins
what are voltage-gated ion channels?
ion channels that open in response to depolarisation
what are ionotropic receptors?
ion channels that open in response to a neurotransmitter binding
what are metabotropic receptors?
can open ion channels via the activation of effector proteins
