Question

Drugs affect the cell function in a variety of ways. Briefly describe and provide an example of an agonist, a competitive antagonist, and a noncompetive antagonist.

Answer 1

Agonist

       * Agonist is a substance that bind to the receptor and produces a response.

       * Agonists can be divided as

                             * Exogenous agonist ( pharmacological drugs which act on specific recptors).

                             * Endogenous agonist (neurotransmitters and hormones in the body which

                                                                   act on specific receptors for action.)

                             * Physiological agonist ( some substances are act on same receptors and produce

                                                             same effect in the body.)

                          Example ; Morphine,Hydrocodone (Activate opioid receptors)

Competitive antagonist

                  * In this the agonist and antagonist compete for the same receptor.this type of antagonism

                    can be overcome by increasing the concentration of agonist so it is also called reverse

                    antagonism.

               Example ; Acetylcholine and atropine are compete at muscarinic receptors.

                                     Acetylcholine and D tubocurarine compete for nicotinic receptors.

Noncompetitive antagonist

                    * It is a type of antagonist which create block at the level of receptor-effector linkage

                      and prevent activation of the receptors.

            Example; Medication Verapamil blocks the cardiac calcium channels and inhibit the

                             entry of calcium during depolarization so it antagonize effect of cardiac stimulants

                              like adrenaline.