1. agonist and antagonist

An agent that binds with receptors and increase its action is called agonist.

1. Agonist: An agent which activates a receptor to produce an effect similar to a that of the physiological signal molecule.

2. Antagonist: A n agent which prevents the action of an agonist on a receptor or the subsequent response, but does not have an effect of its own.

3. Partial agonist: An agent which activates a receptor to produce submaximal effect but antagonizes the action of a full agonist .

4. Inverse agonist: A n agent which activates receptors to produce an effect in the opposite direction to that of the agonist. Ex. beta adrenergic Blocker