Pharmacology of neurotransmitters Flashcards
What are the main types of inhibitory and stimulatory neurotransmitters in the CNS?
STIMULATORY
glutamate
INHIBITORY
GABA
Why is brain pharmacology complicated?
one neurotransmitter has multiple has effects
with many pathways that are interconnected
this is also why drugs modulating CNS pharma are complex and numerous
(unlike peripheral pharmacology)
What are the association between dopamine and disease?
PARKINSON’S DISEASE
reduced dopamine
PSYCHOSIS, SCHIZOPHRENIA
increased dopamine
What is the association between serotonin and disease?
DEPRESSION reduced serotonin (5-HT)
What is the association between GABA and disease?
SEDATION, ANXIETY
increased GABA
What are the main features of a neurotransmitter?
- synthesised in neurons
- stored in vesicles and secreted from neurons
- identity of action: stimulate neurons/receptors should be the same effect as applying NT
- receptors for NT: use of agonists or antagonists
- termination of response: uptake transporters or enzymes
What are the different types of neurotransmitters in the CNS?
AMINO ACIDS
fast mechanism
excitatory, inhibitory
AMINES
slower response than AAs
more involved with modulation of the excitation/inhibition response rather than binary response
NEUROTROPHIC AGENTS
not technically NTs
work in conjunction with NTs to modulate their effects
sometimes these are also secreted from other non-neural cells e.g. immune cells
What are the AMINO ACID types of neurotransmitters in the CNS?
EXCITATORY
glutamate
aspartate
INHIBITORY
GABA
glycine
What is GABA?
-> key inhibitory NT
= gamma-amino-butyric -acid
What are the AMINE types of neurotransmitters in the CNS?
- dopamine
- serotonin (5-HT)
What are types of neurotrophic agents active in the CNS?
- Substance P
- calcitonin-gene related peptide (CGRP)
- vasoactive intestinal peptide (VIP)
- brain-derived neurotrophic factor (BDNF)
released from neurones + other cell types
can act at pre- or post-synaptic sites (do not conform to normal NT rules)
The synthesis of which 2 NTs are interconnected?
glutamate + GABA
this means that changes in glutamate will potentially affect GABA function too
How is glutamate made?
(= NT)
- converted from glutamine released from glial cells, which then enter the neurones
- made from glucose via the Krebs cycle
(so if increased rate of Krebs cycle, increase ate of glutamate synthesis)
How is GABA made?
From glutamate
via glutamic acid decarboxylase (enzyme is required in GABAergic neurons)
What is glutamate?
major EXCITATORY NT in CNS
distributed through the CNS
Binds to:
1) ligand-gated ion channel receptors (fast)
e. g. AMPA, NMDA and kainate
- > binding causes Na+/Ca2+ influx and membrane depolarisation and AP firing
2) GPCR: mGlu (slower response)
both will induce AP firing in subsequent neuron via binding at the post-synaptic membrane
How is glutamate involved in learning and memory?
SYNAPTIC PLASTICITY is the basis for learning/memory
high frequency stimulation of neurons, enhances the synaptic activity
Glutamate -> NMDA -> Ca2+ influx -> synapse function modulated -> basis for learning and memory (hippocampus)
What is glutamate excitotoxicity?
Glutamate is toxic when overexpressed to abundant in the synapses
Removed quickly (glutamate uptake transporters) into glial cells or converted into glutamine in astrocytes
Stroke: ischaemia -> cell death -> necrotic release of glutamate -> hyper-stimulation -> glial cell toxicity
What is the pharma potential of glutamate?
interesting for neurodegeneration
but may have huge side effects
What is ketamine?
non-competitive block/inhibitor of NDMA receptors
(blocks effects of glutamate binding)
- anaesthesia
- recreational
What is GABA?
major INHIBITORY NT in CNS
mainly found in interneurones
Binds to:
1) ligand gated: GABA-A
2) GPCR: GABA-B
What proportion of CNS is GABAergic?
30% of all synapses are GABAergic
What is the purpose of having inhibitory interneurones in the CNS?
provides distinction between different types of excitation
does this by breaking down neural info into levels of excitation (relative to inhibitory signals)
How does GABA-A signalling work?
binds to ligand-gated ion channels
Causes Cl- influx: results in hyperpolarisation -> termination of AP (inhibition)