Drugs on synaptic transmission

Question 1

what are the various steps in neurotransmission

Answer 1

1) synthesis
2) storage
3) arrival of action potential at pre-synaptic bouton
4) depolarisation of terminal to activate vgccs
5) release (calcium dependant)
6) neurotransmitter binds to receptors
7) uptake/breakdown of neurotransmitter

Question 2

what do local anaesthetics and anti epileptics do

Answer 2

they block voltage gated sodium channels so no action potentials can propagate down the axons.

Question 3

what do analgesics do

Answer 3

block voltage gated calcium channels so that neurotransmitters can’t be released

Question 4

where is Ach synthesised

Answer 4

NMJ
ganglia
parasympathetic post-ganglionic fibres
CNS

Question 5

what is the enzyme that synthesises acetylcholine

Answer 5

choline acetyltransferase (ChAT)

Question 6

what is acetyl coA produced by

Answer 6

cellular respiration

Question 7

what are the consequences of ChAT inhibitors

Answer 7

(fa64a)

they are ChAT inhibitors - very dangerous biological weapons - all ganglia would not work and NMJ would not work

Question 8

what does the botulism toxin do (chloristrodium botulism)

Answer 8

degrades Ach containing vesicles so ANS and motor fibres are inhibited

Question 9

what does beta bungarotoxin do

Answer 9

type of snake venom

prevents Act release

Question 10

what is acetylcholine broken down (inactivated) by

Answer 10

acetylcholinesterase (AchE) loaded on post-synaptic membrane

Question 11

what are anti-choline esterases

Answer 11

drugs that enhance on prolong chmlinergic transmission

cause increase in parasympathetic actions e.g. bradycardia, bronchoconstrictoin etc.

Question 12

short actin drugs

Answer 12

e.g. edrophonium
used for diagnostic purposes
improves myasthenia gravis

Question 13

medium acting drugs

Answer 13

e.g. neostigmine

used to reverse neuromuscular block after surgery

Question 14

long acting drugs

Answer 14

irrervsible

new AchE needs to be synthesised and so is very dangerous

Question 15

where is A and NA synthesised

Answer 15

CNS
sympathetic post ganglionic fibres and
adrenal medulla

Question 16

what is the equation to get DOPA decarboxylase

Answer 16

tyrosine + DOPA > DOPA decarboxylase (rate limiting step)

uses tyrosine hydroxylase in cytoplasm

Question 17

how do you get dopamine

Answer 17

DOPA decarboxylase > Dopamine

uses dopamine decarboxylase

Question 18

how do you get NA

Answer 18

Dopamine > NA

uses dopamine hydrolase

Question 19

how do you get A

Answer 19

NA > A

uses PNMT in adrenal medulla

Question 20

how and where is NA stored

Answer 20

in vesicles in a complex with ATP

because ATP is also a nuerotransmiter at noradrenergic synapses

Question 21

what is Resperpine

Answer 21

a drug that disrupts the complex between ATP and NA so that NA leaks out of the cytoplasm
this reduces the ability for vesicles to take up NA
causes a reduction in adrenergic transmission
used as early treatment for hypertension

Question 22

what is guanethidine

Answer 22

an adrenergic neuron blocker

inhibits release of NA

Question 23

how is NA removed

Answer 23

by reuptake unchanged back into pre-synaptic terminal

Question 24

high affinity carrier =

Answer 24

uptake 1 (neuronal sites, ANS, CNS)

Question 25

low affinity carrier =

Answer 25

uptake 2 (non-nueronal sites)

Question 26

how is NA metabolised in neurones

Answer 26

by Monoamine oxidase (MAO)

Question 27

how is NA metabolised in non-neuronal sites (e.g. adrenal medulla)

Answer 27

cathecol-O-methyltransferase (COMT)

Question 28

what drugs may target this uptake mechanisms

Answer 28

Cocaine
tricyclic anti depressant
(inhibit uptake 1 = increase adrenergic transmission)

Question 29

what is MAO inhibitor used as

Answer 29

an antidepressent