Chapter 6 - Neurotransmitter systems Flashcards
What are the 11 elements of neurotransmitter systems?
- Presynaptic axon terminal
- Neurotransmitter-synthesizing enzymes
- Synaptic vesicle transporters
- Reuptake transporters
- Degradative enzymes
- Transmitter-gated ion channels
- G-protein-coupled receptors
- G-proteins
- G-protein-gated ion channels
- Second messenger cascades
- Postsynaptic dendrite
What are cholinergic, noradrenergic, glutamnatergic and peptidergic synapses?
Synapses that use acetylcholine, norepinephrine, glutamate, and peptide, respectively.
What are the criteria for a molecule to be considered a neurotransmitter?
- Must be synthesized and stored in the presynaptic neuron
- Must be released by the presynaptic axon terminal upon simulation
- When experimentally applied, must produce a response in the postsynaptic cell that mimics the response produced by the release of the neurotransmitter from the presynaptic neuron.
What is immunocytochemistry?
Once the neurotransmitter candidate has been chemically purified, it is injected under the skin or into the bloodstream, where it stimulates an immune response. It can be used to localize any molecule for which a specific antibody can be generated, including the synthesizing enzymes for transmitter candidates.
- Molecule of interest is injected into an aminal, causing an immune response and the generation of antibodies.
- Blood is withdrawn, and antibodies isolated from the serum.
- Antibodies are tagged with a visible marker and applied to sections of brain tissue. The antibodies label only those cells that contain the neurotransmitter candidate.
What is in situ hybridization?
A synthetic probe is constructed containing a sequence of complementary nucleotides that will allow it to stick to the mRNA. If the probe is labeled, the location of cells containing the mRNA will be revealed.
Tell a little about studying transmitter release.
Once a transmitter candidate has proven to be synthesized by a neuron and localized to the presynaptic terminal, it must be shown that it is actually released upon stimulation.
Even when it has been shown that a transmitter candidate is released upon depolarization in a calcium-dependent manner, we can’t be sure that the molecules collected in the fluids were released from the axon terminals; they may have been released as a secondary consequence of synaptic activation.
Tell a little about studying synaptic mimicry.
The third criterion for neurotransmitters is that the molecule must evoke the same response as that produced by the release of the naturally occurring neurotransmitter from the presynaptic neuron.
Through microiontophoresis, the transmitter candidate’s effects on the membrane potential can be measured.
Tell a little about studying receptors.
The receptors for various neurotransmitter systems need to be researched.
Three approaches are very useful. Neuropharmacological analysis of synaptic transmission, ligand-binding methods, and molecular analysis of receptor proteins.
What is neuropharmacological analysis?
- Analysis of what effects different drugs have on different parts of physiology.
- Using selective antagonists, to distinguish receptor subtypes.
What are ligand-binding methods?
Any chemical compound that binds to a specific site on a receptor is called a ligand for that receptor. The technique of studying receptors using radioactively or nonradioactively labeled ligands is called the ligand-binding method.
What is molecular analysis?
The structure of the polypeptides that make up many proteins has been determined, and this has shown how much diversity there can be in them. This is a field of molecular neurobiology.
What is Dale’s principle?
The idea that a neuron has only one neurotransmitter. Many peptide-containing neurons violate this. When two or more transmitters are released from one nerve terminal, they are called co-transmitters.
What are cholinergic neurons?
Neurons that have the neurotransmitter Acetylcholine ACh. Its synthesis requires a specific enzyme, ChAT. They also manufacture AChE for degrading ACh.
What are catecholaminergic neurons? Where are they found?
Neurons that contain neurotransmitters that have a chemical structure called a catechol. These are dopamine (DA), norepinephrine (NE) and epinephrine (adrenaline).
These neurons are found in the parts of the nervous system involved in the regulatio nof movement, mood, attention, and visceral function. They all contain the enzyme tyrosine hydroxylase (TH), and dopa decarboxylase.
What are serotonergic neurons?
Neurons containing the amine neurotransmitter serotonin. They are relatively few in number, but appear to play an important role in the brain systems that regulate mood, emotional behavior, and sleep.