serotonin

what type of neurotransmitter is serotonin

indolamine

role of serotonin

• controls mood, appetite, sleep

• regulates cognitive functions including memory and learning

how is serotonin synthesised

from amino acid tryptophan in presynaptic serotonergic neurones

how is serotonin stored and released

stored in vesicles and released by exocytosis

what receptors do serotonin bind to

specific receptors serotonin or 5-HT receptors and produces either excitatory or inhibitory postsynaptic effects

how is serotonin removed from synaptic cleft

by specific serotonin transporters and degraded by enzyme monoamine oxidase

there are 7 different types of 5-HT receptors which serotonin binds once released. what does 5-HT1 receptors do

• coupled to Gi/o heterotrimeric G proteins

• Gi/o activation leads to inhibition in postsynaptic activity via inhibition of adenylyl cyclase

there are 7 different types of 5-HT receptors which serotonin binds once released. what does 5-HT2 receptors do

• 5-HT2 receptors are coupled to Gq/qq G proteins

• their activation leads to excitation or increase in postsynaptic activity via activation of PLC and release of Ca2+ from intracellular stores

there are 7 different types of 5-HT receptors which serotonin binds once released. what does 5-HT3 receptors do

• ligand-gated ion channels 

• activation leads to opening of ion channel permeable to Na+

• leads to depolarisation and increase in postsynaptic activity

there are 7 different types of 5-HT receptors which serotonin binds once released. what does 5-HT4,6,7 receptors do

• coupled to Gs G protein 

• activation of adenylyl cyclase 

• leads to excitation or increase in postsynaptic activity

there are 7 different types of 5-HT receptors which serotonin binds once released. what does 5-HT5 receptors do

• coupled to Gi/o G protein 

• inhibits adenylyl cyclase

• inhibition or decrease in postsynaptic activity 

where is serotonin mainly produced and where does it project

raphe nuclei (midbrain/pons); projects to hypothalamus (appetite), basal ganglia (movement), limbic system (emotion), neocortex (cognition), and spinal cord (anti-nociceptive)

how is serotonin action terminated at the synapse

by the energy dependent process of serotonin transporters

Sodium/ potassium ATPases use energy from ATP hydrolysis to create a concentration gradient of ions across the pre-synaptic membrane. This gradient drives the opening of the transporter and co-transport of sodium and chloride ions and dopamine from the synaptic cleft. Potassium ions binding to the transporter enable it to return to the outward position. Release of the potassium ions into the synaptic cleft equilibrates the ionic gradient across the pre-synaptic membrane

drugs that affect serotonin

• Reuptake inhibitors: fluoxetine (Prozac) → depression, anxiety, OCD

• Hallucinogens: LSD → stimulate 5-HT2A → visual distortions