Depression is a devastating illness that has affected up to 450 million people around the world.The extract from St. John's wort (Hypericum perforatum, SJW), a bushy, wild-growing plant with yellow flowers, has been used for centuries in many folk and herbal remedies. The herbal remedy, SJW has been shown to be as effective as antidepressants in trials in Germany and elsewhere, with no major side effects. Present study proves the involvement of SJW in modulating serotonergic system and also proves that, tryptophan dependency of serotonin function are related to adaptation to conditioned...