Studies involving alcohol and its interactions with other neurotoxicants represent
the focus of several works of research due to the fact that the use of alcohol can
sometimes leads to serious health problems. Fetal exposure to alcohol and mercury
has a high incidence in some regions of Brazil, where there are pregnant women who
are alcoholics and live in mining areas. This work was conducted to examine the effects
of combined exposure to ethanol (EtOH) and methylmercury (MeHg) in rats during the
development of the central nervous system (CNS). Experimental behavioral animal models/tests
were used in order to examine locomotion, anxiety, depression and memory. Pregnant
rats received tap water or EtOH 22.5% w/v (6.5 g/kg per day), by gavage) during pregnancy
and breast-feeding. On the 15th day of pregnancy, some groups received 8 mg/kg of
MeHg (by gavage). The groups were as follows: control, EtOH, MeHg and EtOH+MeHg. The
experimental results showed that the EtOH, MeHg and EtOH+MeHg groups reduced the percentage
of frequency and time spent in the open arms entries of the elevated plus-maze (EPM)
test, when compared to the control group. This result suggests an anxiogenic behavioral
response. The MeHg group increased locomotor activity in the arena and the immobility
time in the forced swimming test, suggestive of depression-like behavior. The EtOH+MeHg
group showed greater reductions in the percentages of frequency and time spent in
the open arms entries in the EPM test, suggesting a sedative-behavior since the frequency
of enclosed arm entries was affected. In the inhibitory avoidance task, the EtOH+MeHg
group reduced the latency of the step-down response onto the grid floor, suggesting
a cognitive and behavior dysfunctions. Taken together, the results suggest that EtOH
and/or MeHg intoxication during the developing CNS may be a risk for deficits related
to locomotor impairment, anxiety, depression and neurocognitive functions. There is
a possibility that EtOH may prevent some of the MeHg responses, but the precise mechanism
of action involved in this process needs to be considered for future research.