lecture 11 LOs Flashcards
where are serotonergic neurons in the CNS found
along the midline of the brain stem associated with the raphe nuclei
where else does serotonin exist (besides the raphe nuclues)
the gut
is serotonin a monoamine
yes, similar to both DA and NE
what is the molecular type of serotonin
indolamine
what is serotonin synthesized from
the amino acid tryptophan
what are the steps of the synthesis of serotonin
tryptophan hydroxylase converts tryptophan to 5-hydroxyl-tryptophan (5-HTP) (rate limiting step)
aromatic amino acid decarboxylase (AADC) converts 5-HTP to serotonin
where can tryptophan be found
only in serotonergic neurons
what does para-chlorophenylalnine (PCPA) do
irreversibly inhibits tryptophan hydroxylase to block serotonin synthesis
what stimulates serotonin synthesis
administration of large doses of precursor (either tryptophan or 5-HTP)
how easily does tryptophan get across the blood brain barrier
it competes with other amino acids for transport across the BBB
the ratio of tryptophan determines the stimulation of serotonin synthesis
how can the levels of serotonin in humans be temporarily decreased
giving an amino acid ‘cocktail’ without the tryptophan in it
what does the tryptophan reducing cocktail do (how does it work?)
it decreases the concentration of tryptophan which decreases the amount of serotonin that can be made
it stimulates synthesis of proteins in the liver which also reduces levels of plasma tryptophan
what does reducing tryptophan through the cocktail result in
reappearance of symptoms in previously depressed patients
behavioural changes like increased impulsivity in healthy subjects
what transports serotonin into vesicles
VMAT2
what is VMAT2 sensitive to
reserpine
what do serotonin autoreceptors on presynaptic terminals do
inhibit release
what do somatodendritic autoreceptors (on raphe central bodies) do to serotonin neurons
slows the firing rates of them
after release, how is serotonin removed from the synapse
reuptake by the serotonin transporter (SERT)
how is the breakdown of serotonin catalyzed
by MAO (mono amine oxidase) to make 5-HIAA