Neurotransmitters Flashcards
What are the three criteria that classify a neurotransmitter?
- They are synthesized and packed in presynaptic neurons
- They are released in axon terminals
- It produces a post-synaptic response
What are the two methods of localization of neurotransmitters?
- In situ hybridization
- Immunocytochemistry
What are the differences in the two methods of localization of neurotransmitters?
In situ hybridization - MRNA probe binding - labels cell bodies, cheap but time consuming
Immunocytochemistry - Antibodies recognize neurotransmitters/enzymes/transport - can label processes, short, sometimes is missing information on the cell body that the axon came from
What two methods of study give information on neurotransmitters in studies using agonsists?
- Micro-ionophoresis: Reproduction of effects using injection of agonist
- Microelectrode - Electric stimulation of a molecule effect on postsynaptic EPSP/IPSP
What are the two types of cholinergic receptors?
- Nicotinergic
- Muscarinic
What do different receptor subtypes differ in other than structure?
They differ in antagonists
What are the three subtypes of glutamatergic receptors?
- AMPA
- Kainate
- NMDA
What are characteristics of ionotropic receptors?
- Rapid synaptic transmission
- Sensitive to molecules and sometimes membrane potentials
- It mediates membrane currents
- It is selective for specific ions
What is the mechanism of synthesis of acetylcholine?
It is made form acetyl-CoA + choline done by choline acetyltransferase
What happens to Acetylcholine in the synaptic cleft?
It is broken down into choline and acetate by acetylcholinesterase
What are the roles of acetylcholine in the body?
It is an effector of motor stimulation, and can be stimulatory or inhibitory in the sympathetic and parasympathetic nervous sytem
What are the three amino acids looked at in class?
- Glutamate
- Glycine
- GABA
What NT is responsible for 80% of excitatory synapses in the CNS?
Glutamate (Glutamic acid)
What is the role of GABA and how is it synthesized?
It is the principal inhibitory synapse NT and is synthesized from glu by Glutamate decarboxylase
What are the two modes of action for Glycine?
- co-activation by glutamate
- It is an inhibitory NT
What is the E of glutamatergic receptors?
0mV
Which glutamatergic receptors are more rapid and are involved in the initial phase of the EPSP?
AMPAR/KainateR
What are the three types of glutamatergic receptor in a glutamate synapse? What subsections of receptors are they in?
AMPAR/KAR, NMDAR = ionotropic
mGluR = metabotropic
The AMPAR/KainateR receptors are permeable to what ions?
K+/NA+
What ion is the plug for the NMDA receptors?
Mg2+
What happens to the membrane voltage of the postsynaptic neuron when there is Mg2+ present in the synapse?
It plugs the NMDA receptors and therefore the cell is “partially depolarized” with a voltage of -35mV
At what voltages are Glutamatergic cells considered depolarized?
above +30mV
What removes the Mg2+ ion from blocking the NMDA receptors?
The depolarization of the cell from the opening of AMPAR
What is the role of NMDAR?
It is a slower, longer phase of the glutamatergic EPSP. It is Ca2+ permeable and is associated with synaptic plasticity
What are the two NTs responsible for inhibitory transmission?
GABA for most, and glycine for non-GABAergic inhibitory action
What do GABARs bind?
Ethanol, benzodiazepine, and barbiturate
When is the reversal of inhibitory synaptic potential with the flux of Cl- ions observed?
-70mV
What is the structure of G-protein coupled reactors?
A single polypeptide with 7 alpha helix transmembrane domains
What types of NTs bind to metabotropic receptors?
Peptides and Amines
What indicates the activation/inactivation of G-proteins?
Activated - bound to GTP
Inactivated - bound to GDP
What are the 5 steps of metabotropic receptor action?
- Floating G-protein
- G protein separates when NT binds into Ggtp and Gby
- The two complexes activate effector proteins
- G hydrolyzes GTP back into GDP and inactivates
- The two parts og the G-protein come back together and reassemble
What is the shortcut pathway of a G-protein action?
The Gby directly opens a potassium channel
What is the cascades of second messengers in G-protein action?
It is the Ggtp protein starting a long cascade of reactions
What is the push pull principle in the cascade of second messengers in metabotropic brain receptors?
It means secondary reactions can inhibit and activate other reactions to create fine tuned responses
What is a possibility of secondary messenger cascades and occurs in the PLC NT?
Cascades can split into multiple branches
What is divergence and convergence of NT signals?
Divergence is the ability of one NT to effects many effectors in a ell and convergence is when one effector is affected by many NTs
