K1vii: Serotonin Receptors
Serotonin = monoamine neurotransmitter
Location of Serotonin:
- CNS & Platelets = 10%
- Enterochromaffin cells of GI = 90%
Serotonin Receptors:
- All GPCR except 5HT3 (ligand gated)
- Effects:
- CNS
- Sleep-wake cycle
- Temperature regulation
- Appetite
- Mood
- Impulsivity
- Anxiety & Depression
- Sexual behaviour
- RESPIRATORY
- Bronchial smooth muscle constriction
- CVS
- Vasoconstriction
- + inotropy & chronotropy
- CNS
Rec
5HT1
Mechanism
GPCR
Gi →↓AC →↓cAMP
SoA
CNS Endothelium
Effect
Inhibits endothelial NO release = cerebral VC
Drugs
Agonist
Sumatriptan
VC to ↓migraine
Rec
5HT2
Mechanism
GPCR
Gq →↑Phospholipase C →↑IP3 + DAG →↑Ca++
SoA
CNS
Pre-frontal
Parietal
Somatosensory
Choroid Plx
GI tract
Plats
Effect
Plat aggregation & VC
Drugs
Agonist
LSD
Antagonist
Risperidone
Rec
5HT3
Mechanism
Ligand gated Na and K channel
SoA
CNS
Area Postrema
NTS (vom centre)
GI Tract
Parasymp nerve terminals
Effect
Emesis
Drugs
Antagonist
Ondansetron
Rec
5HT4
Mechanism
GPCR
Gs →
↑AC →↑cAMP
SoA
CNS
GI
Myenteric Plx
Secretory cells
Effect
GI peristalsis & secretions
Drugs
Agonist
Tegaserod