Question

Drug: labetalol

Molecular target(s) of the drug?

Is the drug a receptor agonist? If yes, what receptor(s)?

Is the drug a receptor antagonist? If yes, what receptor(s)

Does the drug cause vascular smooth muscle contraction or relaxation?

Will the drug inhibit a vascular smooth muscle contraction induced by phenylephrine?

If yes, the action via which one of the following three mechanisms:

(1) the drug inhibits the binding of phenylephrine to its receptor; OR

(2) the drug inhibits the signal transduction induced by phenylephrine; OR

(3) the drug causes vasodilation.

Will the drug inhibit a vascular smooth muscle contraction induced by angiotensin II?

If yes, the action via which one of the following three mechanisms:

(1) the drug inhibits the binding of angiotensin II to its receptor; OR

(2) the drug inhibits the signal transduction induced by angiotensin II; OR

(3) the drug causes vasodilation.

Drug: celiprolol.

Molecular target(s) of the drug?

Is the drug a receptor agonist? If yes, what receptor(s)?

Is the drug a receptor antagonist? If yes, what receptor(s)

Does the drug cause vascular smooth muscle contraction or relaxation?

Will the drug inhibit a vascular smooth muscle contraction induced by phenylephrine?

If yes, the action via which one of the following three mechanisms:

(1) the drug inhibits the binding of phenylephrine to its receptor; OR

(2) the drug inhibits the signal transduction induced by phenylephrine; OR

(3) the drug causes vasodilation.

Will the drug inhibit a vascular smooth muscle contraction induced by angiotensin II?

If yes, the action via which one of the following three mechanisms:

(1) the drug inhibits the binding of angiotensin II to its receptor; OR

(2) the drug inhibits the signal transduction induced by angiotensin II; OR

(3) the drug causes vasodilation.

Drug: clonidine

Molecular target(s) of the drug?

Is the drug a receptor agonist? If yes, what receptor(s)?

Is the drug a receptor antagonist? If yes, what receptor(s)

Does the drug cause vascular smooth muscle contraction or relaxation?

Will the drug inhibit a vascular smooth muscle contraction induced by phenylephrine?

If yes, the action via which one of the following three mechanisms:

(1) the drug inhibits the binding of phenylephrine to its receptor; OR

(2) the drug inhibits the signal transduction induced by phenylephrine; OR

(3) the drug causes vasodilation.

Will the drug inhibit a vascular smooth muscle contraction induced by angiotensin II?

If yes, the action via which one of the following three mechanisms:

(1) the drug inhibits the binding of angiotensin II to its receptor; OR

(2) the drug inhibits the signal transduction induced by angiotensin II; OR

(3) the drug causes vasodilation.

Answer 1

1. Labetalol - is not a receptor agonist . Labetalol is receptor antagonist as it non-selectively antagonizes beta-adrenergic receptors, and selectively antagonizes alpha-1-adrenergic receptors. It causes vascular smooth muscle relaxation and not contraction by acting on alpha adregenic receptors to block it and partially blocking beta adrenergic receptors leading to vascular dilation . Yes the drug inhibit vascular muscle contraction induced by phenylephrine as phenylephrine acts as or mimics action of epinephrine and norepinephrine and cause vascular muscle contraction whereas labetalol block the alpha adrenergic receptor and induce vascular dilation and thus inhibiting as antagonist . . Thus Correct option is 3. - drug causes vasodilation.

Other options are incorrect as explained how inhibit vascular contraction induced by phenylephrine . Option 1 is inhibit binding to receptor but labetalol act on alpha adrenergic and in option it is already binded to the site as stated " induced by" thus not inhibiting binding of phenylephrine.Option 2 is also incorrect as doesn't inhibit signal transduction.

( Number of question is done as directed and time permitted)

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