In the present study, memory loss was observed among mice
having blood lead levels between 62 and 69 g/dL together
with brain lead levels between 2.4 and 2.9 g/g tissue protein.
The recorded blood lead levels were consistent with the wellestablished
threshold for neurotoxicity (Adonaylo and Oteiza,
1999), which were achieved 8 weeks after maintaining of mice on
drinking water containing lead at 1 g/L. We have also shown that
the sign of lead poisoning such as memory loss can be alleviated
by co-treatment with vitamin E or aqueous leaf extract of Thunbergia
laurifolia Linn. (Figs. 1 and 2). However, neither vitamin E
nor TL extract however produced effects on levels of lead accumulation
in blood and brain. These results suggested that TL extract
or vitamin E by itself had no chelating effects. Most likely, the
mechanism(s) underlying protective effects of TL extract involve
improvement on total anti-oxidant capacity, maintenance of antioxidant
enzyme activity in the brain together with reduction of
cell loss because of accelerated caspase-3 activity (Tables 4 and 5).
Increase in oxidative stress has been shown to cause alterations in
brain structure, behavioral abnormalities and learning impairment
(Alfano and Petit, 1981; Petit et al., 1983; Ryter et al., 2007). Cotreatment
with TL extract was found to ameliorate oxidative stress
and reduce cell death