serotonin Flashcards
serotonin (5-HT)
monoamine neurotransmitter that influences many physiological and behavioral processes
where is 5-HT located?
peripheral 5-HT controls gut mobility and initiates peristaltic and secretory reflexes
tryptophan
an essential amino acid that cannot be synthesized by organisms
tryptophan hydroxylase
rate limiting enzyme in serotonin synthesis
rate limiting step of central 5-HT synthesis
passage of tryptophan across BBB
TPH1
expressed by 5-HT secreting cells in the gut and melatonin-secreting cells in the pineal gland
TPH2
expressed by 5-HT secreting
neurons
where is tryptophan hydroxylase found?
in a series of cell groups in the brainstem called the Raphe Nuclei
5-HT receptors
serotonin receptors are a large group of G protein coupled receptor (mostly) and
ligand-gated ion channels found in both the brain and periphery
types of receptors
7 families and 14 sub-types
- 5-HT1A,1B,1D,1E,1F
- 5-HT2A,2B,2C
- 5-HT3* *Ionotropic
- 5-HT4
- 5-HT5A,5B
- 5-HT6
- 5-HT7
5-HT1A location
concentrated in the hippocampus, septal area, amygdala and dorsal raphe nuclei
5-HT1A
- reduce cAMP synthesis by
inhibiting adenylyl cyclase - increase opening of K+ channels and membrane hyperpolarization
- similar activity to D2 and a2 (alpha 2) receptors
- leads to decrease cell firing in post-synaptic cell (post-synaptic
receptor) or serotonergic neuron itself (auto-receptor)
5-HT2A location
throughout the brain with a large number in the (neo)cortex
5-HT2A
- primarily responsible for activating phosphoinositide 2nd messenger system
- increases Ca2+ influx into
postsynaptic cells - activated protein kinase C (PKC)
release and inactivation
- terminal autoreceptors directly inhibit 5-HT release
- somatodendritic autoreceptors indirectly inhibit 5-HT release, by slowing the rate of neuron firing.
5-HT autoreceptors are typically
5-HT1A, 5-HT1B or 5-HT1D subtypes
