L5- CNS: Transmitters & Receptors (Amino Acids) Flashcards
(18 cards)
What is the MAIN excitatory neurotransmitter in the CNS?
Glutamate
What is the MAIN inhibitory neurotransmitter in the CNS?
GABA (in the BRAIN)
Glycine (In the SPINAL CORD)
What are two types of Glutamate Receptors?
Explain how they differ from each other
Ionotropic (iGLuR)
- Lignad-gated cation channels
- Fast-Acting
- Mediate synaptic transmission
Metabotropic (mGluR):
- G-protein coupled receptors
- Slow-Acting
- Modulate synaptic transmission
What are the types of ionotropic receptors for Glutamate?
NMDA
- Initiate G-protein coupled signaling
- Slower action
Non-NMDA: AMPA/kainate
- Pass ionic currents
- Fast action (msec)
Why do we not want Glu in our synapse?
Brain Ischemia is due to increased release of glutamate (from increased Ca2+ influx)
- Due to lack of electro-gradient, the transporters cannot work to take up Glu (and may even depolarize and release Glu instead)
What are AMPA Receptors?
A subclass of IONOTROPIC receptors that mediates the majority of fast excitatory synaptic transmission
- gate primarily Na+
4 Subunits: GluA1, GluA2, GluA3, GluA4 (A stands for AMPA lol)
What is the consequence of AMPA receptors lacking the GluA2?
Higher permeability to Ca2+
→ excessive amounts of Ca2+ produced can result in cell death (excitotoxicity)
What blocks NMDA Receptors?
They are blocked by Mg2+
In normal transmission, infrequent synaptic activity:
- Glutamate mainly activates AMPA receptors and there is not enough glutamate to activate metabotropic receptors and the NMDA receptor is blocked by Mg2+
How do you UNBLOCK NMDA Receptors?
An intense, REPEATING stimuli would increase the release of glutamate that is enough to activate metabotropic receptors
→ Sustained depolarization in cell → Mg2+ is picked off → OPENS NMDA channel!!
- This INCREASES Ca2+ in channel and lead to changes in synaptic strength
*Which of the following mediates the majority of fast excitatory synaptic transmission in the CNS?
a. NMDA receptors
b. AMPA receptors
c. Metabotropic glutamate receptors
d. GABA receptors
e. Glycine receptors
b. AMPA receptors
*Which of the following is NOT an endogenous excitatory amino acid?
a. Glutamate
b. Aspartate
c. Glycine
d. Kainic Acid
e. None of the above
d. Kainic Acid
*Transport of glutamate between glial cells and neurons can be dangerous. How do glia solve this problem?
a. Degradation of glutamate by glutamate hydrolase
b. Conversion of glutamate to glutamine by glutamine synthetase
c. Inhibition of glutamate reuptake by glutamate transporters
d. Conversion of glutamate to GABA by glutamic acid decarboxylase
e. None of these answers are correct
b. Conversion of glutamate to glutamine by glutamine synthetase
*Inhibition of GABA receptors might cause
a. Seizure effects
b. No effects
c. Sedative effects
d. Muscle relaxation
e. None of the above
a. Seizure effects
NMDA receptors are blocked at resting membrane potential because of
A. Low concentration of extracellular magnesium
B. Magnesium in the channel pore
C. Calcium influx through the receptor
D. Sodium influx through the receptor
E. None of the above
B. Magnesium in the channel pore
Transport of glutamate between glial cells and neurons can be dangerous. How do glia solve this problem?
A. degradation of glutamate by glutamate hydrolase
B. conversion of glutamate to glutamine by glutamine synthetase
C. inhibition of glutamate reuptake by glutamate transporters
D. conversion of glutamate to GABA by glutamic acid decarboxylase
E. None of the above
B. conversion of glutamate to glutamine by glutamine synthetase
Activation of GABA receptors might cause:
A. seizure effects
B. Convulsant effects
C. Sedative effects
D. All of the above
E. none of the above
C. Sedative effects
Metabotropic mGluRs are distinguished from iGluRs in the following ways
A. mGluRs are relatively slow-acting, iGluRs are fast-acting
B. mGluRs modulate synaptic transmission, iGluRs mediate synaptic transmission
C. mGluRs couple to G proteins, iGluRs are ion channels
D. All of the above
E. none of the above
D. All of the above
Glutamate, the main excitatory neurotransmitter in the CNS, is involved in all of the following functions except:
a. Excitotoxicity
b. Modulation of other neurotransmitters
c. Protein catabolism
d. Plasticity
e. Fast synaptic transmission
c. Protein catabolism
