Neurotransmitters and specific antidepressants Flashcards
What are the two broad categories of neurotransmitters?
- Small molecule
2. Neuropeptide
What type of neurotransmitters are biogenic amines?
small molecule
What are the 4 characteristics to be a Neurotransmitter?
- present in the presynaptic neuron
- released in response to presynaptic
depolarization - receptors for the substance must be
present of the postsynaptic cell - Has a method for signal termination
List the Catecholamines
- Norepinephrine
- Epinephrine
- Dopamine
List the Indoleamines
serotonin
What are Indoleamines and Catecholamines?
Monoamines
what type of NT are Gamma-aminobutyric acid (GABA), glutamate, and glycine?
Amino acids
What type of NT is Acetylcholine?
Quaternary amine
where is Acetylcholine found?
– Skeletal muscle
– Vagus nerve and heart
– Autonomic nervous system – Central nervous system
What are 2 important sybtypes of Acetylcholine receptors? where are the found?
– Nicotinic – ligand-gated ion channel, mainly in
muscle
– Muscarinic – metabotropic, found in ANS, CNS
What are 2 important sybtypes of Acetylcholine? where are the found?
– Nicotinic – ligand-gated ion channel, mainly in
muscle
– Muscarinic – metabotropic, found in ANS, CNS
List the Biogenic Amines
dopamine, norepinepherine, epinepherine, serotonin, histamine
List the Biogenic Amines
dopamine, norepinepherine, epinepherine, serotonin, histamine
Describe the general lifecycle of non-peptide neurotransmitters?
- Precurser reacts with enzymes to produce neurotransmitter
- Packages into vesicles
- Released into synapse
- Transporter brings them back into presynaptic neuron
what is a cholinergic neurons?
a neuron that primarily uses Acetylcholine
Where are cholinergic neuron cell bodies primarily located?
where do their axons project to?
Cell bodies located:
- spetal nuclei
- nucleus basalis
axons project to:
- forebrain (in particular hippocampus and cerebral cortex)
Is Acetylcholine excitatory or inhibitory?
excitatory
Biosynthesis of the catecholamines begins with which amino acid?
tyrosine
How are catecholamines inactivated?
primarily through reuptake into the presynaptic nerve terminal
Norepinephrine and epinephrine act on which two primary types of receptors
alpha and beta
Dopamine exerts postsynaptic effects on which recpetors?
At least 6 in 2 categories
What are the precursors to Acetylcholine?
Acetyl Co A and Choline
+ the enzyme choline acetyl transferase
Excitatory neurotransmitters have what effect of the post synaptic neuron
depolarizing
How is Acetylcholine terminated?
Broken down by an enzyme and its (acetate and choline)
by an enzyme called
Acetyl-cholin-esterase
then those compontents are brought back into the presynaptic neuron to create more acetlcholine
Where are the cell bodies of norepinephrine neurons located?
in the brain stem, mainly in a structure in the pons called the locus coeruleus
axons project widely throughout the brain to nerve terminals in the cerebral cortex, the limbic system, the hypothalamus, and the cerebellum
also travel down the spinal cord, where they exert an analgesic action
What are the 2 important subtypes of Acetlycholine recpetors?
Nicotinic – ionotpropic,
mainly in muscle
Muscarinic – metabotropic, found in ANS, CNS
what enzymes catabolize dopamine and norepinepherine?
Mononamine Oxidase (MAO) and
Catechol-O-Methy Transferase (COMT)
Where do dopamine cell bodies originate? where do they send signals?
brain stem, sending axons both rostral (forward) to the brain and caudal (backward) to the spinal cord
dopamine receptors are all?
metabotropic
What type of NT is serotonin?
Indoleamines
What is the amino acid precursor to serotonin?
tryptophan
What are the two enzymes involved in serotonin production?
tryptophan hydroxylase and amino acid decarboxylase
What are serotonin receptors called?
5-HT receptors
which 5-HT receptor should drugs NOT interact with
5-HT 2B receptors are thought to cause heart problems, it has been nicknamed the “death receptor”
What is the precurser to GABA?
what enzymes are involved?
a different neurotransmitter (glutamate)
enzyme glutamic acid decarboxylase
How is glutamate synthesized?
many ways BUT important
= the glutamine cycle
- after glutamate has its effect in the synapse it is transported and converted to the inactive glutamine by astrocytes
eventually it diffuses into the nerve terminal where it is converted back to glutamate
What types of Glutamate receptors exist?
- ionotropic
- metabotropic
For a glutamate NMDA receptor to be activated what needs to be present
glutamate but ALSO
either glycine or serine
What is the full name of GABA?
Gamma Aminobutyric Acid
Where are dopaminergic cell bodies located?
Where do they project to (describe the 3 circuits we will focus on)
Located in:
Substantia nigra and project to -> caudate nucleus of the basal ganglia and is involved in motor functions
Located in:
Midbrain (NEXT to Substantia nigra) and project to -> that project widely to the cerebral cortex and forebrain limbic system
Where are norandrenergic cell bodies located? where do they project?
Located in: locus coeruleus and adjacent regions of the brain stem
Project widely to the forebrain and cerebellum and to the brain stem and spinal cord.
Serotonin involved in?
Regulation of sleep and wakefulness, mood, circadian rhythms, feeding behaviour, nausea, pain, blood pressure, motor control, sexual behaviour, impulsivity, aggression
Histamine involved in?
Associated with arousal and attention in the CNS
Norepinepherine involved in?
Associated with sleep and wakefulness, attention, and feeding behaviour
Dopamine involved in?
Involved in motor control, motivation, reward, and reinforcement
List the different types of antidepressants
- TCAs: tricyclic antidepressants
- MAOIs: monoamine oxidase inhibitors
- Heterocyclic
- SSRIs
- SNRIs
- NDRI (wellbutrin)
- SEROTONIN-2 ANTAGONISTS/REUPTAKE INHIBITORS (SARIs)
Mechanism of action of TCAs?
- They block the presynaptic reuptake transporter for norepinephrine and serotonin.
- TCAs block postsynaptic receptors for histamine and acetylcholine. Such blockade accounts for most of the side effects of this class of drugs.
What is a major drawback of TCAs?
Blocks histamine: drowsiness
Blocks acetylcholine,
Blocks alpha adrenergic: drop in blood pressure
+slow onset
major drawback of MAOIs?
toxicity, need for dietary restrictions
irreversable
