Effects of baicalin on morphine-induced behavioral sensitization in mice

Objective To investigate the effects of baicalin on morphine-induced behavioral sensitization. Methods Locomotor activity was measured for 2h after administration with baicalin in mice. Hyperlocomotion induced by acute morphine (10 mg·kg-1, ip) and behavioral sensitization induced by repeated morphine were established. The level of dopamine of ventral tegmental area(VTA) and prefrontal cortex(PFC) in mice was tested by ELISA assay. Results Baicalin inhibited significantly both locomotor activity in mice(control (1095.8±174.5)times, baicalin(899.6±187.2), (724.2±221.4), (609.1±154.6)times; P<0.01) and hyperlocomotion induced by acute morphine(model (1518.2±185.8)times, baicalin(1385.4±224.2), (1205.1± 174.6), (1100.3±235.1)times; P<0.01). Similar inhibition was also seen in the development and expression of morphine-induced behavioral sensitization(model(2096.2±304.6) times, baicalin(2004.2±218.5), (1998.7± 224.3), (1836.1±233.5)times, P<0.05; model(2124.2±189.6)times, baicalin(1922.2± 314.7), (1524.1±289.2), (1477.4± 219.3) times, P<0.01). Baicalin inhibited dopamine release in VTA and PFC of morphine-sensitized mice(model(457.6±92.1, 589.2 ±102.5)μg·L-1, baicalin(391.1±56.8)μg·L-1, (448.6± 99.3)μg·L-1; (324.5±66.2)μg·L-1, (368.7±45.9)μg·L-1; (234.3± 52.6)μg·L-1, (305.3±84.1) μg·L-1; P<0.01, P<0.01). Conclusion Baicalin inhibits the development and the expression of morphine-induced behavioral sensitization in mice, and this effect is related to the inhibition of dopamine release in VTA and PFC of mice. Key words: Baicalin; Morphine; Behavioral sensitization; Dopamine