Neuropharmacology (Neurotransmission) Flashcards
What is the fundamental property of all drugs that act on the CNS?
They all must cross the BBB
How do drugs cross the BBB?
- Drug is lipophilic/amphoteric
- Transporters present for drugs
- BBB becomes leaky due to pathology
What is volume transmission?
As opposed to fast transmission mediated by some neurotransmitters at closely opposed synapses, some NTs are released from varicosites and diffuse longer distance before acting on target post-synaptic receptors.
What is the role of glutamate in CNS?
Main excitatory NT
How is glutamate synthesised?
- α-ketoglutarate (TCA cycle) →(Glutamate dehydrogenase)→ Glutamate
- Transamination with another amino acid as -NH2 donor
How is Glu transported into vesicles?
- VGLUT1 & VGLUT2: Ubiquitous in all cells
- VGLUT3: Limited distribution
What are the effects of reduced VGLUT1 activity?
- Anxiety
- Depression
- Reduced long-term memory
What are the effects of reduced VGLUT2 activity?
- Reduced neuropathic pain
- Schizophrenia-like symptoms
- Reduced anxiety
How is Glu transmission terminated?
Transport into surrounding glial cells and post-synaptic neurone
What mediates Glu transport into cells?
Excitatory amino acid transporters (EAATs)
What are the types of EAATs?
- EAAT-1,2 (glial cells)
- EAAT-3,4 (post-synaptic neurones)
- EAAT-5 (retina)
How can EAAT action be disrupted?
- Disrupting Na+ gradient
- Disrupting membrane potential
- Disrupting K+ gradient
All these factors contribute to providing energy for EAAT action
What is the Glutamate-glutamine cycle?
What are the types of Glu receptors?
Ionotropic:
- AMPA
- NMDA
- Kainate
Metabotrophic: mGluR
What is the structure of AMPA Glu receptors?
- Tetramer
- Each subunit has 4 TM domains
- Glu binding site between N-terminus and TM3/TM4 loop region
- TM2 makes up selectivity filter (?)
What needs to happen for AMPA Glu receptors to be activated?
Binding of Glu onto all 4 subunits
What is the ionic specificity of AMPA receptors?
Na+ & K+
How many different types of AMPA subunits are there?
4 (GluA1-4)
What are the event that occur following continuous stimulation of the AMPA receptors?
- Desensitisation due to rearrangement of subunits
- Deactivation due to removal from PM
What is the structure of Glu kainate receptors?
- Tetramer
- Pre-synaptic and post-synaptic
What is the ionic specificity of kainate receptors?
Ca2+
What are the functions of pre-synaptic kainate receptors?
- High [Glu] → -ve feedback of Glu release
- Low [Glu] → +ve feedback of Glu release
How many different types of kainate subunits are there?
5 (GluK1-5)