Neurotransmitters Flashcards
What are the two types of purinergic receptors?
P2X (ionotropic)
P2Y (GPCR)
How are NDMA glutame receptors activated?
- Has a voltage dependent Mg block
- Needs a slight increase in voltage from Na in through the AMPA channel to displace
- Permeable to to Na, Ca, K
What does MAO-A degrade?
Noradrenaline and 5-HT
How is GABA formed?
From glutamate by the enzyme GAD (glutamic acid decarboxylase)
What are opiates?
- Drugs derived from the opoid poppy
- Morphine, heroin
What is the Mesocorticolimbic system involved in?
- The ‘reward’ system
Where is GABA present in the body?
Cerebral cortex and striatum
Neruopeptide neurotransmitters?
Substance P
Enkaphalin
Endorphins
What are the 4 diffuse modulatory systems of the brain?
- Acetylchonine
- Dopamine
- Serotonin
- Norepinepherine
What does the basal forbrain complex do?
- Regulates brain excitability during arousal and sleep/wake cycles
- Role in memory and learning (first to die in Altzhiemers)
What does GABA allow through?
Cl - produces IPSPs
How is 5-HT synthesised?
1) Tryptophan –> 5-HTP (by tryptophan hydroxylase)
2) 5-HTP –> 5-HT (by 5-HTP decarboxylase)
What are endocannabinoids?
- Endogenous forms of canabis used as neurotransmitters
- Don’t require synaptic vesicles
- Bind to GPCR
What is the marker for glutamanergic receptors?
The glutamate receptors AMPA, NDMA, kainate
- Can’t be glutamate as it is used to make peptides and is found in every neuron
What are the 2 diffuse cholenerigic complexes in the brain?
1) Basal forebrain complex (several related neurons)
- Medial septal nucleus (send projections into the hippocampus)
- Basal nucleus of Mayenert (send projections into the neocortex)
2) Pontomesencephalotegmental complex
- In pons and midbrain complex
Where are the neurons in the Nigrostriatal pathway and where do they project?
- In the substansia nigra
- Project into the sriatum
What is the main excitatory neurotransmitter in the body?
Glutamate
What is the marker for cholinergic neurons?
ChAT (choline acetyltransferase)
What are the 2 dopaminergic diffuse pathways in the brain?
1) Nigrostriatal pathway
2) Mesocorticolimbic
Where is 5-HT released from and where does it project to?
- Released from raphe nuclei (group of nuclei all along brainstem)
- Each nuclei project into a different region of the brain
Where are opiod receptors present?
In nociceptive areas:
1) Dorsal columns
- Blocks pain sensation to brain
2) Periaqueductal grey
- Pain
3) Amygdala
- Emotional response to pain
4) Frontal cortex
- Cognitive pain
5) Bran stem (medulla oblongata)
- Cough reflex
- Depress respiration
What does the 5-HT diffuse system modulate?
- Pain-related sensory signals
- Sleep/wake cycles
- Mood
- Emotional behaviour
What does the synthesis of 5-HT start with and how is this obtained?
Tryptophan, obtained from the diet, moves from the gut –>blood –> Extracellular fluid –> presynaptic vesicles
How is ATP used as a neurotransmitter?
- Packaged into vesicles as a co-transporter (never present on its own)
- Binds to purinergic receptors
What is the marker to show GABA neurons?
GAD (glutamic acid decarboxylase)
What is Dale’s principle was it correct?
- One neuron has one neurotransmitter
- Was incorrect as cotransporters
Why become addicted to drugs that enhance the Mesocorticolimbic pathway?
- Motivated to perform behaviors that stimulate this pathway
- Like the feeling that the drugs give - reward
Which MAO enzyme degrades dopamine?
MAO-B
What does the noradrenergic diffuse system regulate?
Attention Arousal Sleep/wake Learning/memory Anxiety/pain Mood
How is acetly choline synthesised?
- From acetyl-CoA and choline
- By enzyme ChAT (choline acetyltransferase)
Where does the diffuse noradrenergic system come from?
- Locus coeruleus (one little nucleus) in the pons
- Innovates nearly all of the brain
Amino acid neurotransmitters?
Glutamate (excitatory)
GABA (inhibitory)
Glycine (inhibitory)
Aspartic acid
Amine neurotransmitters?
5-HT (Serotonin)
Histamine
acetylcholine
Catecholamines
- Dopamine
- norepinepherine
- epinerpherine
How are catecholamines degraded?
1) COMT in cytoplasm of presynaptic membrane
2) MAO in the outer mitochondrial membrane
- MAO-A
- MAO-B
What are diffuse modulatory systems?
- Core of each system has a small set of nuclei (often in the brainstem)
- No synapses, neurotransmitter released into the extracellular fluid
- Regulate functions rather than specific tasks
- Neurotransmitter can contact 100,000 postsynapic neurons across the brain
What neurotransmitter type are opiods?
Peptide hormones, formed in the RER
What are the therapeutic uses of opiods?
1) Analgesia
- Reduce perception and emotional response to pain
2) Intestinal disorders
3) Stop coughs
Where are the axons in the Mesocorticolimbic pathway and where do they project?
- Neurons in the ventral tegmental area (in the midbrain)
- Project into the frontal cortex and limbic system
What receptors type are the opoid receptors?
GPCR - inhibitory G protein
What are endorphins?
Naturally occuring opoids
How is acetyl choline degraded?
- By acetylcholinesterase in the synaptic cleft
- Broken down into acetic acid and choline
How are catacholamnies synthesised?
1) TYROSINE –> L-Dopa (by tyrosine hydroxylase)
2) L-Dopa –> Dopamine (by dopa decarboxylase in presynaptic terminal)
3) Dopamine –> Norepinepherine (by dopamine B-hydroxylase in synaptic vesicles)
4) Norepinepherine –> epinepherine (By PNMT in cytosol)
What are opoids?
A broad class of natural and synthetic compounds - Including endorphins, enkephalins, dynophin
What does the Nigrostriatal pathway facilitate?
- Voluntary movement
- Degeneration = Parkinsons
Problems with opiods?
Tolerance Dependance Sedation Constipation Respiratory depression
What prevents the release of Ach and how?
- Botulinum toxin (BOTOX)
- Degrades SNARE proteins, preventing vesicle release
