Part 1: Synthesis, Release, Inactivation

What are the three catecholamines?

DA, NE, Epi

Are the catecholamines, monamines

Yes

What are the four steps in catecholamines synthesis

Tyrosine, then synthesized by enzyme 1 (tyrosine hydroxylase) to DOPA then DA then NE then EPI

What is the negative feedback loop of catecholamines synthesis

An increase in catecholamine decreases tyrosine hydroxylase

What is the rate limiting component of catecholamine synthesis?

Tyrosine hydroxylase

What are the functions of DA, NE, and EPI, separately?

DA: movement and reward

NE: emotion and increasing heart rate

EPI: increasing heart rate

What is VMAT? And what is the difference between VMAT 1 and VMAT 2?

VMAT is a monoamine transporter that recognizes monoamine and transports to vesicles for release

VMAT 1: EPI and NE

VMAT 2: NE, EPI, and DA

How do autoreceptors inhibit catecholamine release?

Decrease neuron firing by opening volt gated K+ channels and decrease chance of an AP and decreases Ca 2+ influx

What do agonists do in regard to catecholamine release?

Stimulate the autoreceptors and decrease the amount of catecholamine release

What are two ways catecholamine is inactivated

1. Reuptake

2. Enzyme Degradation

Explain how reuptake inactivates catecholamine and the name of the transporters

DA and NE move from synaptic cleft into nerve terminal

DAT → remove DA from synaptic cleft

NET → NE transporter

What drug inhibits monoamine reuptake

Cocaine

Is serotonin a monoamine? Is it a catecholamine?

Serotonin is a monoamine but not a catecholamine

Steps of serotonin synthesis

Tryptophan (found in soy, corn, and turkey) is then synthesized by enzyme trypt. Hydroxylase and then 5 HTP becomes serotonin

What is the rate limiting component of serotonin synthesis?

Tryp hydroxylase

Can tryptophan enter the BBB? How can the ratio of tryptophan increase

Tryptophan can’t enter the BBB w/o a transporter and it competes with other AA.

Eating a low protein high carb diet may increase the tryptophan ratio to cross BBB more and increase serotonin synthesis

What does MDMA (ecstasy) do to serotonin levels?

Depletes serotonin

This can be used to treat PTSD

In high doses there is no recovery

What is the receptor that loads serotonin into vesicles for release?

VMAT 2, this is the same for DA and NE

What transport mediates the reuptake of serotonin during inactivation?

SERT

What is an example of some drugs that block the reuptake of serotonin

Prozac blocks it selectively

Cocaine does but is not selective, also effects DA