Question

1. Recall the sites (effectors) of alpha₁-, beta₁-, and beta₂-adrenergic receptors and state the expected responses from their activation by a suitable agonist.
2. Explain the difference between direct cardiac (beta₁) effects of adrenergic agonists and reflex (baroreceptor reflex–mediated) effects of those same drugs, using norepinephrine, phenylephrine, and isoproterenol as examples.
3. Identify the desired effects when a therapeutic dose of epinephrine is given for anaphylaxis and explain the actions of the drug that earn it the label “drug of choice” for anaphylaxis.
4. Discuss the rationale for the limited applications of mecamylamine.

Answer 1

Q. No 1. Answer :

Sites of alpha 1 adrenergic receptors are smooth muscles cells of blood vessels of the skin, gastrointestinal system, kidney, and brain.

The expected response is by activation of this receptors by suitable agonist is Vasoconstriction ,that means these are activated by Epinephrine or norepinephrin, so it increases the blood pressure and returning blood flow to the heart.

Sites of beta 1 adrenergic receptors are located in heart, when these are stimulated the heart rate increases and contractility may strengthen.

Sites of beta 2 adrenergic receptors are broncheoles of the lungs and arteries of the skeletal muscle .

When the activation of beta 2 adrenergic receptors leads to relaxation of the smooth muscles of the lungs and dilatation and opening of the airways.

Q. No 2. Answer

Difference between direct cardiac effects of adrenergic agonists and reflex effects of those same drugs :

* adrenergic agonists are drugs these are stimulates the responses from adrenergic receptors.

* where as reflex receptors or baroreceptors found in aorta and carotid sinus, which will show direct changes in our blood pressure, if our blood pressure increases the walls of the arteries stretches and stimulates increased activity in baroreceptors.

* so here norephinephrin and phenylephrin will increases the blood pressure. So the baroreceptors activity may increases.

Q. No 3. Answer :

Desired effects of Epinephrine as a therapeutic dose for anaphylaxis :

* anxiety,

* Restlessness,

* Tremors,

* weakness,

* Dizziness

* palpitations

* pallor

* Nausea

* vomiting

* sweating

* headache and

* respiratory difficulties.

Action of the drug :

Alpha adrenergic receptors and epinephrine decreases the vasodilatation and increases the vascular permeability it leads to loss of intravascular fluid volume and hypotension. During in anaphylaxis.

Q. No 4. Answer :

Mecamylamine used to treat moderate to severe and severe to high blood pressure.

* it is used like a ganglionic blocker.

* and it have many side effects like dilated pupils, blurred vision, drowsiness, dizziness, dry mouth, difficulty in urination and constipation and, nausea and vomiting.

* and not only this it will lowering the blood pressure by blocking the alpha 3 beta 4 nicotinic receptors in the brain and it will affects on autonomic nervous system.

So thats way it is limited application.