sympathathetic nerve system

Sympathetic nerve system (adrenergic neurons):
These Ns found in CNS and Sympathetic nerve system(between ganglia and effecter organs
Synthesis of neurotransmitter ( nor epinephrine):
1- synthesis:
Tyrosine inter neuron by Na linked carrier converted to DOPA by tyrosine hydroxylase then to dopamine by decarboxylase enzyme

2- storage:
Dopamine enter the vesicle by carrier( which is blocked by reserpine ( an alkaloid block Mg++-ATP dependant transport of biogenic amine , nor epinephrine , dopamine , serotonin from cytoplasm into storage vesicle)).

In vesicle dopamine converted to nor epinephrine by dopamine ?- hydroxylase enzyme
Adrenal medulla synthesized & storage nor epinephrine 15% and epinephrine 85% .
Nor epinephrine is protected from degradation of MAO in the vesicle.

3- release:
Action potential trigger an influx of Ca++ from extra cellular fluid to axoplasm leading to fusion of vesicle with cell mem.
This release is blocked by Guanithidine

4-binding to a receptor:
The neurotransmitter bind with pre and post synaptic receptors after diffusion in synaptic cleft , the effect produced by G-protein coupled receptor

5- removal of nor epinephrine :
It metabolized by COMT and MAO in the synaptic space **
COMT: catechol-o-methyl transferase
MAO: monoamine oxidase
**reuptake by neuronal mem by ( Na – K- activated ATPase that can be inhibited by TCA such as Imipramine or by cocaine .

6- the metabolite of are excreted in urine


*inhibitory auto receptors
* inhibitory hetero receptors