Neurotransmitters and Neuromodulator Flashcards
Ionotropic
These receptors are ion channels. Muti-unit channels that form a poor
- Neurotransmitter binds
- Channel opens
- Ion flows acrosse membrane
RAPID ACTING MECHANISM (either depolarization/repolarize)
Example: Ligand gates ion channels
Metabotropic
Require secon messenger pathway
“SLOW ACTING”
(phosphorylate/dephosphorylate channel)
- Neurotransmitter binds
- G-proteins is activated
- G-proteins subunits or intracellular messengers modulae ion channels
- Ion channels flow
- Ions flow across membrane
Where are neurotransmitters found?
Synthesized in the neuron and present in the presynaptic terminal, and its release exerts a defined action on the post synaptic cell
When a neurotransmitter is administered exogenously, it mimics what?
Mimics the action of the endogenous chemical
(same effect in the lab as in the body)
What are the different processes that can occur to remove neurotransmitters from the synaptic cleft?
Reuptake
degradation
diffusion
What are the diffeent type of neurotransmitters?
Small molecule transmitters
Neuropeptides
Steroid Hormones as Neuromodulators
What are the different type of Small molecule neurotransmitters?
•Amino acid neurotransmitters:
glutamate
GABA
glycine
•Brain stem neurotransmitters:
acetylcholine
biogenic amines (brain stem monoamines)
catecholamines: dopamine, norepinephrine
Indoleamines: seratonin
What are the different types of Neuropeptides?
Opiods
tachykinins
gastrins
What is Glutamate?
it is a amino acid transmitter
Predominant excitatory NT in the the CNS (ALWAYS)
Has a widespread distribution of neurons and receptors (Pyramidal cells of the cerebral cortex)
Released at about 90% of CNS synapses
How is Glutamate removed from the synaptic cleft?
Via diffusion (since it is a very small molecule)
and
glial uptake
Glutamate is involved in what pathway of the body?
Involved in synaptic plasticity
Long term potentiation, long term depression
What two medical conditions involve Glutamate?
Seizures (neurons firing out of control) and epilepsy.
Excitotoxity
Glutamate - Ionotropic Receptors
•NMDA RECEPTORS (big player in cytotoxity)
Binding site for glutamate, NMDA, and glycine
Permeabel to Cations (Na+, Ca2+, K+) , rapid depolarization
Blocked by Mg2+ at resting membrane potential (so initial depolarization stimulus is required to get ion out. Glutamate has to first act at one of the other two receptors to start depolarization)
- AMPA RECEPTORS
- KAINATE RECEPTORS
Glutamate - Metabotropic Receptor
• Metabotropic glutamate receptors may be on the presynaptic neuron (autoregulation, self binding after release of glutamate), on the post-synaptic neuron, or on glia cells.
What is GABA?
It is a amino acid transmitter
Glutamate -> “Gamma-aminobutyric acid” (loss of carboxygroup)
(enzyme = Glutamic acid decarboxylase)
•Predominant inhibitory neurotransmitter in the CNS
Caused chlorine influx
•Widespread distribution of neurons and receptors
Lots of interneurons are GABA
How is GABA removed from the synaptic clet?
Via Diffusion
What are the Pharmocological drugs that utilize GABA?
Benzodiazepines - antianxiety (Valium and Xanax)
anti-anxiety
Barbiturates
anesthesia
(makes it harder for neurons to fire because they are hyperpolarized)
“Highly Adictive”
GABA Ionotropic Receptor
GABAA Receptors
- Binding sites for GABA, benzodiazepines, barbiturates.
- Permeable to chloride ions, hyperpolarization
Cause hyperlorization and make it more diffictul to have a AP
GABA Metabotropic Receptor
GABAB Receptor
(have to subunits that work together - allosteric modulation. B1 binds GABA and then activate B2, which is the G protein couple part that will hyperpolarize the neuron)
- Dimerization, “allosteric modulation”.
- Actions through G-protein mechanisms
- Increased K+ conduction, hyperpolarization
What is acetycholine?
It is a brainstem neurotransmitter
(Produced in the Pedunculopontine nucleus and Nucleus basalis)
• Implicated as playing a role in cognition and learning.
Acts through nicotinic (ionotropic, excitatory/neuromuscular junction)
or
muscarinic (metabotropic; excitatory or inhibitory/Second messenger pathways) cholinergicreceptors.
• Synthesized by choline and a actetly group with the help of choline acetyltransferase. Choline is not biosynthesized and must be obtained through the diet.
How is excess acetycholine degraded?
degraded in the synapse by the enzyme acetylcholinesterase
Acetycholinesterase inhibitors is clinically used to help manage which disease?
Myasthenia Gravis
What is Dopamine (DA)?
It is a catecholamine that falls under brainstem monoamines
•Dopamine exerts its actions through metabotropic receptors (primarily D1 and D2).
D1 receptor activation stimulates adenylyl cyclase (excitatory).
D2 receptor activation inhibits adenylyl cyclase (inhibitory).
What is the Nigrostriatal pathway
Dopamine pathway from Substantia Nigra to basal nuclei (basal ganglia)
“Dopamine nuerons that dies in Parkinson’s”
Describe the cinical symptoms and pathology hallmarks of Parkinson’s Disease?
Clinical symptoms
- Hypokinetic movement
- Cogwheel rigidity
Pathology hallmarks
- Nigrostriatal degeneration
- DA neuronal degeneration in substantia nigra
The Nigrostriatal Pathway is affeced
What is the Mesolimbic pathway?
Dopomanine receptors from the ventral tegmental area to the nucleus accumbens to the prefrontal cortex
involved with motivation and reward. It is heavyly implicated in addiction.
Norepinephrine goes through what synthesis before is becomes norepinephrine?
It goes through dopamine synthesis
(enzyme is Dopamine Beta-hydroxylase)
What is Norepinephrine?
It is a Catecholamine that is classified as the brain stem monoamine.
•primarily involved in stress and arousal, but is also implicated in higher cognitive functions.
Widespread distribution
•Its actions are exerted through alpha and beta adrenergic receptors.
Metabotropic receptors, excitatory or inhibitory depending on the receptor subtype and on the target cells.
How is norepi removed from the synaptic cleft?
Presynaptic reuptake mechanism
(uptake proteins on the pre-synaptic terminal)
Monoamines synthesiszed in the nerve terminal
What is the basis of Indolamines?
Tryptophan based
What is Seratonin (5-Hydroxytryptamine)?
It is an Indolamine (Brain stem monoamine)
Alson known as 5HT
- Involved in mood, and heavily implicated in anxiety disorder and depression.
- Actions are exerted through multiple subtypes of metabotropic receptors, which may cause excitatory or inhibitory responses.
How is Seratonin (5HT) removed from the synaptic cleft?
Presynaptic reuptake mechanism
Reuptake inhibitors (SSRIs) cause there to be more 5HT in the synaptic cleft, how does that affect the body?
Change Mood
SSRI are effective in treating mood disorders
Small molecule transmitters
Site of Synthesis
Type of Vesicle
Mechanism of Release
Release and Replenishment
Site of Synthesis: Synthesized locally in nerve terminalis
Type of Vesicle: smaller “lucent” vesicles
Mechanism of release: Localized release at active zone, “docking” recycling of vesicles
Release and Replenishment: Release can be rrapid and sustained
Neuropeptides
Site of Synthesis
Type of Vesicle
Mechanism of Release
Release and Replenishment
Site of Synthesis: Synthesized in cell body (ribosomes) (require protein sythesis and need gene)
Type of Vesicle: Large ‘dense core’ vesicles (have Leucent and dark vesicles)
Mechanism of Release: “Secretory Pathway” not localized to active zone, no recycling of vesicles
Release and Replenishment: slower secretory release (Metabotropic), slower replenshment
Peptides co-transmit with what?
Peptides and small molecule transmitters typically coexist in the same neuron and are released together (co-transmission)
Types of Neuropeptides
Edorphines - pain killers (inhibitory)
Tachykinins - pain transmitters (excitatory)
Somatostatin - hypothelamic peptide (inhibitory)
Cholecystokinin - brain gut peptide (excitatory) - inhibit appetite
Nuerotransmitters
Source
Receptors
Mechanism of action
Speed and duation of actions
Source: Released from presynaptic nerve terminals
Receptors: Bind to membrane receptors (ionotropic and metabotropic)
Mechanism of Action: Ion flow or second messenger signaling alters membrane potential
Speed and duration of actions: Rapid, acute, localized actions
Steroid Hormone
Source
Receptors
Mechanism of action
Speed and duation of actions
Source: Circulate in the blood stream (can cross the BB)
Receptors: diffuse into cell to bind intrecellular receptors (receptor in the cell)
Mechanism of action: “Genomic signalin” alters transcription of hormone-responsive genes (transcription factor turning genes on and off)
Speed and duation of actions: Slow, extended, “global” actions
ONLY LIMITING FACTOR - DO YOU OR DONT YOU HAVE THE RECEPTOR TO EXPRESS
Organizational Effect of Steroid Hormones
“There are Sex diffences in the brain”
- Early development exposure to gonadal steroids. Permanetly shape hormone-sensitive brain circuits
- Shape the neurocircuitry that controls reproductive functions (male shuts down ovulation center)
- Widspread effect developin limbic and cortical Systems
- sex difference in cognitive task:
- males have hot spot of intense activity and female have widspread activity with math
- better performance by males with 3-D puzzles
- females are more intune to suttle difference like color change
What is the default brain?
The default brain is female. So the organizational effects that occur in development typically happen in males.
“burst of testosterone exposure”
Activational Effects of Steroid Hormones
- After Puberty
- Females hormones flunctuate/Cyclic, male hormones are more steady
- Receptor dependent
- Adrenal Steroids
- Hippocampus is affected by Cortisol (high levels are neurotoxic)
- Gonadal Steroids
- Limbic System is affected by Estrogen, Testosterone, and Progesterone (impact mood)
What are the activation effect of adrenal Steroids in the brain?
- A number of studies in the last several years have confirmed a strong connection between stress, high cortisol levels, damage to the hippocampus and memory.
- This connection shows up across a wide range of human medical conditions including post-traumatic stress disorder, Cushing’s disease, and depression.
Which disorders are more likely in men than women?
- Autism
- Early onset schizophrenia
- Alcoholism
- Antisocial personality disorder
- ADHD
Which disorders are more common in women than men?
- Depression
- Anxiety disorder
- Somatic complaints
- PTSD
- Alzheimer’s disease
Most neurotransmitters are what type?
Small molecule neurotransmitters
In the CNS how does Glycine behave?
It is excitatory
This type of NT begins with Tyrosine?
All catecholamines
(enzyme Tyrosine hydroxylase convertes Tyrosine to L-DOPA, which is the precursor for dopamine)
Dopamine does not cross the BBB so how can you treat a patient with Parkinson’s?
You give the L-DOPA which can cross the BBB and then it is converted to Dopamine
Norepinephrine is converted to epinephrine? Where is this completed?
Made in the adrenal gland
Where is norepinephrine made?
In Bilateral nuclei called Locus Coeruleus (pigmented neurons that are blue) that are located in the PONS.
Seratonin is found in the brianstem just like dopamine. It is produced by which type of nuclei?
Raphe Nuclei
(Nuclei along the midline around the midline, ventrally and dorsally)
