Synthetic agonists have a similar shape to the natural chemical and so produce the same effect, they mimic the endogenous chemical. Agonists can be both specific or non-specific. Many receptors have slightly different versions of themselves located in different parts of the body which are a slightly different shape to one another. This means that if a drug is 'specific' it will only bind to the particular receptor where the effect is desired. For example, salbutamol will bind to the beta-two receptors on the bronchioles (a type of adrenergic receptor) but will not bind to adrenergic alpha-one receptors on the blood vessels, this
helps to minimise side effects.