NEW YORK, Nov 09 (Reuters Health) -- The discovery of a new chemical pathway in the brain shows that antidepressant drugs can use more than one pathway to alter mood, California researchers report.
The new pathway also suggests that brain chemicals called 'neurosteroids' play a role in controlling anxiety and depression -- making them a promising target for new types of psychiatric drugs.
Newer antidepressants, known as selective serotonin reuptake inhibitors (SSRIs), besides affecting the levels of the chemical serotonin in the brain, increase brain levels of neurosteroids. Scientists have suggested that changes in neurosteroid levels may play a role in premenstrual syndrome (PMS), and, in fact, some SSRIs have provided relief of PMS symptoms, according to Drs. Lisa D. Griffin and Synthia Mellon from the University of California, San Francisco. Their research is reported in the November 9th issue of the Proceedings of the National Academy of Sciences.
The investigators studied the effects of three SSRIs -- Prozac (fluoxetine), Zoloft (sertraline), and Paxil (paroxetine) -- on the production of a neurosteroid (allopregnanolone) by different types of cells in the laboratory and compared them to the older antidepressant, Tofranil (imipramine).
According to the report, the SSRIs increased the activity of a critical enzyme needed to produce allopregnanolone by 10 to 30 times, whereas Tofranil had no effect on the enzyme.
The investigators suggest that these results may enable scientists to design drugs that affect the two forms of the enzyme in specific ways that might improve the treatment of depression, PMS, and other mood disorders.
