4. Acetylcholine and co Flashcards
acetylcholine synthesis
acetyl co A and choline by ChAT - choline acetyl transferase which is used for histological staining
acetylcholine breakdown
cholinesterases into constituents in synapse and then reuptaken
ACh CNS structures:
magnocellular forebrain (nucleus basalis of meynertand septohippocampal pathway) and the brainstem (pedunculopontine and laterodorsal tegmentum) also striatal interneurons in rats but not humans (for movement)
what is ACh for?
attention and arousal
ACh CNS structures are
species dependent - rats ave striatal interneurons that we don’t have
Septohippocampal pathway
projects from the forebrain to the hippocampus - is important in short term memory and learning
NbM
Projects to the cotrex and also to the inhibitory layer of cells just above the thalamus - thalamic reticular nucleus - involved in general arousal
brain stem ACh
sleep wake cycles (cholinergic input –> thalamus = wake state) and motor activity
ACh receptors
nicotinic and muscarinic
Nicotinic ACh receptors
pentamers (homo or heteromeric) - fast EPSPs - Na/K or Ca permeability changes - move large hydrophobic residues out of channel pore and replace with small aqueous residues to form a pore lining - usually presynaptic to facilitate glutamate release
metabotropic ACh receptors
M1,3,5, - E (Change NA perm)
M2,4 - I (change K/Ca perm)
more widespread
Excitatory mAchRs
use the M current. wont generate an AP on their own but a small sustained current instead. If a stimulus is applied during the M current it’ll fire a train of action potentials. it synaptic sensitivity.
Histamine synthesis
synthesise from histadine by histadine decarboxylase (only 64000 cells)
histamine metabolism
broken down by histmaine methyltransferase to methylhistamine and the broken down by MAO
histamine projects to
thalamus!! cortex, amygdala, hypothalamus - the system is more developed in lower mammals - switch on and off in wake and sleep state (discrete)