Cellular communication 5 Flashcards
The NMDA receptor has binding sites for: (select 3)
a. gamma-aminobutyric acid
b. glutamate
c. propofol
d. ketamine
e. magnesium
f. calcium
b. glutamate
d. ketamine
e. magnesium
The amino acid neurotransmitters include:
glutamate
GABA
glycine
__________________ is the primary excitatory neurotransmitter in the brain
Glutamate
______________ is the main inhibitory neurotransmitter in the brain
GABA
_____________________ is the primary inhibitory neurotransmitter in the spinal cord and lower brainstem
Glycine
Glutamate and GABA are interconvertible through
Krebs cycle intermediates
Glutamate receptors can be
ionotropic or metabotropic
NMDA and AMPA receptors are ___________ receptors
ionotropic glutamate
Neuronal injury initiated by excessive glutamate receptor activity is called
excitotoxicity
The glycine receptor is
ionotropic
GABA receptors can be
ionotropic or metabotropic
In a glial cell, glutamate is converted into
glutamine by the enzyme glutamine synthetase
The three types of ionotropic glutamate receptors are named for
the pharmacologic agents that activate them
The three types of ionotropic glutamate receptors are:
- NMDA
- Kainate receptors
- a-amino3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors
Full activation of AMPA receptors requires the binding of
two glutamate molecules
AMPA receptors have ________________ synaptic transmission
fast-gating (rapid) excitatory
AMPA receptors are highly permeable to _________ and poorly permeable to
Na+; Ca2+
Full activation of NMDA receptors requires the binding of
two glutamates
two glycine molecules
a depolarizing voltage change
NMDA receptors are highly permeable to ______________ and poorly permeable to ________
Ca2+; Na+
NMDA receptors have ________ synaptic transmission
slower-gating (delayed)
Metabotropic glutamate receptors are classified into three groups:
group 1 receptors are couple to Gq- they activate phospholipase C
group 2 & 3 receptors are couple to Gi- they prevent the formation of cAMP
Increased released or decreased uptake of glutamate can lead to a positive feedback cycle involving increased
intracellular Ca2+, cellular damage and further glutamate release
Too much of a good thing (intracellular Ca2+) leads to
neuronal injury or neuronal death by apoptosis
Neuronal injury initiated by excessive glutamate receptor activity is called
excitotoxicity
Excitotoxicity is implicated as a pathologic mechanism in many diseases including
Huntington’s disease
Alzheimer’s disease
ALS
stroke & trauma
hyperalgesia
epilepsy
The amount of GABA in the CNS correlates to the amount of
functional GAD (glutamic acid decarboxylase- which catalyzes glutamate to GABA)
How is glycine formed?
glycolysis–> serine–> glycine
Glycine is taken up from the synaptic cleft by
neurons through a glycine transporter
Mutations of the glycine receptor are involved in a rare neurological disease
human startle disease or hyperekplexia
Human startle disease is characterized by
temporary muscle rigidity in response to unexpected stimuli
At resting membrane potential, magnesium channels block _____________ receptors.
NMDA
What two binding sites are located in the NMDA receptor channel (pore)?
Mg2+
ketamine/PCP
Which GABA receptor is metabotropic?
GABAb
Glutamate is converted to GABA by what type of enzymatic reaction?
decarboxylation
Which enzymes are required to degrade epinephrine to vanillymandelic acid? (select 2)
a. catechol-O-methyltransferase
b. L-amino acid decarboxylase
c. monamine oxidase
d. tyrosine hydroxylase
a. catechol-O-methyltransferase
c. monamine oxidase
What are the five biogenic amine neurotransmitters?
dopamine
norepinephrine
epinephrine
serotonin
histamine
Dopamine, norepinephrine, and epinephrine are collectively known as
catecholamines
All biogenic amine neurotransmitters are derived from __________ by ________________ & ____________________
amino acids; hydroxylation & decarboxylation (there is an exception)
The rate-limiting step in catecholamine biosynthesis is
tyrosine hydroxylase
Degradation of NE & epi is carried out by two enzymes:
monoamine oxidase
catechol-O-methyltransferase
The end-product of catecholamine metabolism is
vanillymandelic acid
Serotonin is syntheized from
tryptophan
Histamine is synthesized from
histidine
___________________ is the end-product of serotonin metabolism.
5-hydroxyindoleacetic acid
The biogenic amines elicit a wide range of physiologic responses in the periphery and in the CNS including:
central control of cardiac function, BP, and metabolism
coordination of movement
cognitive function
regulation of appetite & feeding
sleep
behavior
The exception of biogenic amine transmitter receptors being metabotropic receptors is the
ionotropic 5-HT3 serotonin receptor
What two enzymatic reactions are common in the biosynthesis of biogenic amine neurotransmitters?
hydroxylation
decarboxylation
What is hydroxylation?
add an -OH group
What is decarboxylation?
removes a CO2 group
MAO-A preferentially degrades
dopamine, epinephrine, and serotonin
MAO-B degrades
dopamine more rapidly than serotonin and norepinephrine
The most common screening test used to establish the diagnosis of pheochromocytoma is:
catecholamine metabolites in the urine
Dopamine is metabolized by
both MAO & COMT
The major metabolite of dopamine is
homovanillic acid (HVA)
High levels of 5-HIAA in the urine are consistent with
carcinoid tumors
