YEN-YIN LIU¹, PEN-HO YEH¹, GUEI-JANE WANG², SENG-WONG HUANG³, CHIN-WEN CHI^1,4, LI-KANG HO¹ AND WYNN H.T. PAN^1*

1. Institute of Pharmacology, School of Medicine, National Yang-Ming University,
155, Sec. 2, Lee-Nung St., Pei-tou Dist., Taipei City, Taiwan, ROC
2. National Research Institute of Chinese Medicine, Taipei City, Taiwan, ROC
3. School of Medicine, National Yang-Ming University, Taipei City, Taiwan, ROC
4. Department of Medical Research and Education, Taipei City, Veterans General Hospital

(Received: June 16, 2006; Accepted: August 30, 2006)

ABSTRACT

   The potential for neuroprotection by baicalein (5,6,7-trihydroxyflavone), a major constituent from the root of a widely used Chinese medicinal herb Scutellaria baicalensis Georgi, against methamphetamine-induced neurotoxicity was studied. All ICR mice were treated by 4-times repeated intraperitoneal administration, at 2 hr intervals, of either methamphetamine (5 mg/kg), saline, baicalein (1 mg/kg) or baicalein pretreatment followed by methamphetamine. In the striatum of mouse, the tissue level of dopamine was monitored on day 3 and nitric oxide was assayed after 1 hr, 24 hrs and 3 days of the above treatments.  The results showed that striatal dopamine was significantly depleted by methamphetamine and elevated by baicalein. Pretreatment with baicalein prevented the methamphetamine-induced dopamine depletion.  Nitric oxide was depressed by methamphetamine, elevated by baicalein, but remained suppressed with baicalein plus methamphetamine after 1 hr post-treatment.  At 24 hrs nitric oxide concentration was unaffected by methamphetamine but was significantly elevated by baicalein or baicalein plus methamphetamine administration. On 3 days post-treatment nitric oxide was elevated by methamphetamine, baicalein and further markedly elevated by the administration of baicalein plus methamphetamine.  These results suggest a potential neuroprotective role for baicalein with the possible involvement of nitric oxide.