Neurotransmitters Flashcards
Classify neurotransmitters according to structure & function
S, amino acids, biogenic amines, neuropeptides & others
F, excitatory, inhibitory or both
Mention methods of inactivation of neurotransmitters and therapeutic application
Reuptake, SSRI
Hydrolysis, MAO inhibitors
Mention the principal excitatory and principal inhibitory NT and their method of removal
E, glutamate, reuptake
I, GABA, converted to succinate semialdehyde by GABA-T, then oxidized to succinate which is used in Krebs cycle.
Describe formation of GABA
Derived from glutamic acid by glutamic acid decarboxylase enzyme and pyridoxal phosphate is required as a coenzyme.
Describe function, origin and fate of glycine
Major inhibitory NT
Can be synthesized from serine by serine hydroxymethyltransferase, removed by reuptake through high-affinity transporters.
Write equations of synthesis & degradation of Ach
S, Acetyl CoA + choline —ChAT—-> Ach + CoA
D, Ach—-AChE—>acetate + choline
…..is the precursor of catecholamines, while the enzyme directly producing dopamine is …….
Tyrosine
Dopa-decarboxylase
…..is the rate-limiting step of CA synthesis
Tyrosine hydroxylase
The enzyme catalyzing formation of NE ……, While that catalyzing formation of E
Dopamine beta-hydroxylase
Phenyl-ethanolamine N-methyl-transferase
Fates of catecholamines
1- Active uptake by sympathetic nerve endings
2- Catabolism to biologically inactive products by MAO & COMT
D to homovanillic acid
NE & E to vanillylmandelic acid
GR: Occurrence of Parkinson’s & mention a lab result
Due to insufficient production of dopamine as a result of idiopathic loss of dopamine-producing cells in the brain.
Decreased HVA in urine
…..is used to treat Parkinson’s
L-DOPA
Justify the addition of carbidopa to L-dopa
It is an inhibitor of dopa-decarboxylase and reduced the decarboxylation of L-dopa in peripheral tissues thus allowing higher concentration of the precursor to reach the brain.
Alpha-methyl dopa mechanism
Competitive inhibition of DOPA decarboxylase
Mention drug treatment of pheochromocytoma and mechanism
Alpha-methyl tyrosine
Competes with tyrosine for enzyme tyrosine hydroxylase