Week 4 - topic 2

Question 1

Drugs that affect synaptic transmissions are categorised as

Answer 1

Antagonists: A drug that opposes or inhibits the effects of a particular neurotransmitter on the postsynaptic cell.

Agonists: A drug that facilitates the effects of a particular neurotransmitter on the postsynaptic cell.

Question 2

Drugs can influence synaptic transmission by

Answer 2

• Serving as a precursor

- Inhibiting the synthesis of a neurotransmitter

Question 3

Drugs serve as precursor

Answer 3

• Neurotransmitters are synthesized from precursors
• Drugs can act as precursors
• Agonist effect > L-DOPA can be administered as a drug to help synthesize the neurotransmitter dopamine

Question 4

Drug inhibits NT synthesis

Answer 4

• Neurotransmitter synthesis from precursors is controlled by enzymes
• Antagonist effect > drug inactivating an enzyme
  It will prevent the neurotransmitter from being produced.

Question 5

Effects on storage and release of neurotransmitters

Answer 5

• look up image
  3. Drugs can prevent the storage of neurotransmitter in vesicles
  4. Drugs can stimulate the release of neurotransmitter into the synapse
  5. Drugs can prevent the release of neurotransmitter into the synapse

Question 6

Antagonist action (step 3)

Answer 6

• Neurotransmitters are stored in synaptic vesicles
• Vesicle transporter molecules are located in the membrane of synaptic vesicles which pump neurotransmitter molecules across the vesicle membrane, filling the vesicles
• Vesicle transporter molecules can be blocked by drugs

Question 7

Agonist action (step 4)

Answer 7

• Drugs can facilitate the release of neurotransmitters from the terminal button.
• Bind with proteins that cause synaptic vesicles to fuse with the presynaptic membrane and release neurotransmitter into the cleft

Question 8

Antagonist action (step 5)

Answer 8

• Drugs can prevent the release of neurotransmitters from the terminal button
• Deactivate the proteins that cause synaptic vesicles to fuse with the presynaptic membrane and release neurotransmitter into the cleft

Question 9

Drug effects on receptors

Answer 9

6) Drugs can stimulate postsynaptic receptors
7) Drugs can block postsynaptic receptors
8) Drugs can stimulate autoreceptors and inhibit neurotransmitter synthesis/release
9) Drugs can block autoreceptors and stimulate neurotransmitter synthesis/release

Question 10

Competitive binding

Answer 10

Drugs act directly on the neurotransmitter binding site on opening of the ion channel.

1) Direct agonist - Binds with a receptor site that a neurotransmitter would normally bind with- causes postsynaptic potentials (PSPs - Step 6)
2) Receptor blocker (direct antagonist) - Binds with a receptor site that a neurotransmitter would normally bind with - does not cause PSPs (Step 7)

Question 11

Noncompetitive binding

Answer 11

Drugs act on an alternative binding site and modify the effects of the neurotransmitter on opening of the ion channel.

3) Indirect agonist - Binds with a site on a receptor that a neurotransmitter does not bind with, but facilitates the action of the receptor (Step 6)
4) Indirect antagonist - Binds with a site on a receptor that a neurotransmitter does not bind with, but interferes with the action of the receptor (Step 7)

Question 12

Autoreceptor stimulation - and drug effects

Answer 12

Stimulation of autoreceptors normally cause less neurotransmitter to be released

5) Antagonist drugs stimulate autoreceptors and inhibit the synthesis/release of neurotransmitter (Step 8)
6) Agonist drugs block autoreceptors and increases synthesis/release of neurotransmitters (Step 9)

Question 13

Drug effects on Reuptake and destruction of neurotransmitters

Answer 13

10) Drugs can block reuptake of neurotransmitter from the synaptic cleft
11) Drugs can inactive enzymes involved in enzymatic deactivation of a neurotransmitter

Question 14

Reuptake

Answer 14

Molecules of neurotransmitter are taken back into terminal button

Question 15

Enzymatic deactivation

Answer 15

Destruction of a neurotransmitter in synaptic cleft by an enzyme

Question 16

Drugs impact synaptic transmission by influencing neurotransmitter reuptake

Answer 16

Molecules of the drug attach to transporter molecules which are responsible for neurotransmitter reuptake and inactivate them.

This means that neurotransmitters can’t bind and be taken back into the cell (Step 10).

• results in neurotransmitter being left in the synaptic cleft and therefore is an agonist - facilitating post synaptic effects as the neurotransmitter can continue stimulating post synaptic cell

Question 17

Drugs impact synaptic transmission by influencing neurotransmitter deactivation

Answer 17

Molecules of the drug bind to enzymes that normally deactivate the neurotransmitter – stopping enzyme action (Step 11).

• results in neurotransmitter being left in the synaptic cleft and therefore is an agonist - facilitating post synaptic effects as the neurotransmitter can continue stimulating post synaptic cell