receptor
Agonist
antagonist
a1
Norephinephrine
Phenylephrine
a2
Phenoxybenzamine
Prazosin
B1
Clonidine
Yohimbine
Norephinephrine
Propranolol
Epinephrine
Metoprolol
Isoproterenol
Dobutamine
B2
Epinephrine
Proranolol
Norepinephrine
Butoxamine
Isoproterenol
Albuterol
Nicotinic
Ach
Curare
Nicotine
Hexamethonium
Muscarinic
Ach
Atropine
Assume all the chemicals in the table are available to you.
You are given a piece of smooth muscle tissue, you stimulate it with Norepinephrine and find the muscle responds with contractions. Your hypothesis is that the muscle contraction is caused by the activation of α1 adrenergic receptors. Now you need to design an experiment protocol to test your hypothesis.
Background knowledge: The figure below is an experiment setup, the red tissue in the organ bath is the smooth muscle tissues. In this kind of experiment smooth muscle tissue is minimally stretched vertically by two hooks or clips in the organ bath filled with physiological saline solution (PSS). Agonist is added to the PSS to challenge the muscle tissue, muscle contraction is sensed by a force transducer at the top and force is recorded by a computer. Adding antagonist before adding agonist blocks agonist action. PSS may or may not be changed, it depends on your purposes, e.g. if you want to block a type receptors, then you do not want change PSS after you add antagonist to the PSS. Your correct step is that you add antagonist to PSS, wait some time, and add agonist, you keep both antagonist and agonist in the PSS so that you can judge if the receptor blockage by antagonist abolish the agonist action.
The key to this assignment is that you eliminate possible cross-activities of agonists. Cross-activity means an agonist activate more than one types of receptors, you need block each type of the receptor in order to see what type of the receptor is activate to cause contraction. This muscle tissue can have both α and β receptor types and their subtypes, you need to demonstrate convincingly that you only stimulate α1 receptors.
Write an experimental protocol to demonstrate your work, for each step in the protocol you write the chemical(s) you add, why you add, what result you are expecting to see e.g. contract, relax, no response. If the step is to wash the tissue with fresh PSS, then you do not need to indicate the responses.
Here is an example of the answer.
step
chemical added
response
1.
epinephrine, activate alpha and beta receptors,
blood vessel ring contract slightly.
2.
wash with PSS
3.
alpha receptor antagonist and norepinerphine, block NE activating alpha receptor.
blood vessel ring should not contract.
4.
wash with PSS
5.
â¦
â¦
6.
â¦
â¦
Discuss your protocol to show the relation between activation of α1 receptors and the vascular smooth muscle contraction.Design the experiemnt and its conclusion/ results.
| receptor | Agonist | antagonist | |
| a1 | Norephinephrine | Phenylephrine | |
| a2 | Phenoxybenzamine | Prazosin | |
| B1 | Clonidine | Yohimbine | |
| Norephinephrine | Propranolol | ||
| Epinephrine | Metoprolol | ||
| Isoproterenol | |||
| Dobutamine | |||
| B2 | Epinephrine | Proranolol | |
| Norepinephrine | Butoxamine | ||
| Isoproterenol | |||
| Albuterol | |||
| Nicotinic | Ach | Curare | |
| Nicotine | |||
| Hexamethonium | |||
| Muscarinic | Ach | Atropine |
Assume all the chemicals in the table are available to you.
You are given a piece of smooth muscle tissue, you stimulate it with Norepinephrine and find the muscle responds with contractions. Your hypothesis is that the muscle contraction is caused by the activation of α1 adrenergic receptors. Now you need to design an experiment protocol to test your hypothesis.
Background knowledge: The figure below is an experiment setup, the red tissue in the organ bath is the smooth muscle tissues. In this kind of experiment smooth muscle tissue is minimally stretched vertically by two hooks or clips in the organ bath filled with physiological saline solution (PSS). Agonist is added to the PSS to challenge the muscle tissue, muscle contraction is sensed by a force transducer at the top and force is recorded by a computer. Adding antagonist before adding agonist blocks agonist action. PSS may or may not be changed, it depends on your purposes, e.g. if you want to block a type receptors, then you do not want change PSS after you add antagonist to the PSS. Your correct step is that you add antagonist to PSS, wait some time, and add agonist, you keep both antagonist and agonist in the PSS so that you can judge if the receptor blockage by antagonist abolish the agonist action.
The key to this assignment is that you eliminate possible cross-activities of agonists. Cross-activity means an agonist activate more than one types of receptors, you need block each type of the receptor in order to see what type of the receptor is activate to cause contraction. This muscle tissue can have both α and β receptor types and their subtypes, you need to demonstrate convincingly that you only stimulate α1 receptors.
Write an experimental protocol to demonstrate your work, for each step in the protocol you write the chemical(s) you add, why you add, what result you are expecting to see e.g. contract, relax, no response. If the step is to wash the tissue with fresh PSS, then you do not need to indicate the responses.
Here is an example of the answer.
| step | chemical added | response |
| 1. | epinephrine, activate alpha and beta receptors, | blood vessel ring contract slightly. |
| 2. | wash with PSS | |
| 3. | alpha receptor antagonist and norepinerphine, block NE activating alpha receptor. | blood vessel ring should not contract. |
| 4. | wash with PSS | |
| 5. | ⦠| ⦠|
| 6. | ⦠| ⦠|
Discuss your protocol to show the relation between activation of α1 receptors and the vascular smooth muscle contraction.Design the experiemnt and its conclusion/ results.
