Effects of ketamine on brain monoamine levels in rats.

The effects of ketamine (50 mg/kg i.p.) on brain monoamines, including epinephrine, norepinephrine, dopamine, serotonin and its metabolite 5-hydroxy indoleacetic acid, were studied in three groups of male Sprague-Dawley rats. A rapid, simple, accurate, and sensitive spectrophotoflurometric method was developed to determine monoamines extracted from rat brain. Ketamine significantly increased brain epinephrine (25%), serotonin (28%) and 5-hydroxy indoleacetic acid (32%) in rats. In contrast, norepinephrine (43%) and dopamine (58%) levels were significantly reduced at 30 minutes. The increase in epinephrine (13%) and decrease in norepinephrine (31%) and dopamine (38%) levels remained significant 12 hours after ketamine injection. Serotonin and 5-hydroxy indoleacetic acid levels returned to almost normal in ketamine pretreated animals after 12 hours. Thus, the ability of ketamine to interfere with monoamine metabolism was revealed.