The cause of fibromyalgia is unknown; however, it is believed to involve a combination of genetic and environmental factors with half the risk attributed to each. The condition runs in families and many genes are believed to be involved.
Agonist: A substance that acts like another substance and therefore stimulates an action. Agonist is the opposite of antagonist. Antagonists and agonists are key players in the chemistry of the human body and in pharmacology.
On the other hand, antagonists though help in binding receptors, they do not alter its activity. When agonist is a compound that impersonate the action of neurotransmitter, antagonist blocks the action of neurotransmitter. Agonists combine with other chemical substances and promote some action.