Objective To examine the effects of maternal exposure to nicotine by subcutaneous injection on the development and behavior of offspring rats.
Methods Twenty-four pregnant rats were randomly divided into four groups and treated with nicotine saline at 0, 1.0, 2.0, 4.0 mg/kg daily through subcutaneous injections started at the seventh day of pregnancy until the pups were born. General indicators (weight, umbilical cord prolapse, ears open, tooth eruption, and eyes open), early reflex, ability of le arning and memory, and synaptic ultrastructure in hippocampus neurons in the pups were observed.
Results The pups' weights in the experiment groups were significantly inferior to the controls' (P<0.05, P<0.01). The time of ears open was (3.41& #177;0.44) d for the control group and (4.43& #177;0.47) d for the 4.0 mg/kg group (P<0.05). The time of tooth eruption was (10.98& #177;1.21) d for the control group and (13.11& #177;1.14) d for the 4.0mg/kg group (P<0.05). The time of eyes open was (13.56& #177;1.02) d for the control group and (15.89& #177;1.20) d for the 4.0 mg/kg group (P<0.05). The qualified rates of early reflex indicators of the control pups at day 4 and day 7 were significantly higher than those of each experimental group. In Morris water maze, the escape latency was (39.66& #177;8.54)s for the control group, (55.96& #177;8.51)s for the 2.0 mg/kg group, and (58.99& #177;7.66)s for the 4.0 mg/kg group; the time spent in targeted quadrant was (41.22& #177;6.23)s for the control group, (33.25& #177;6.98)s for the 1.0 mg/kg group, (30.33& #177;8.21)s for the 2.0 mg/kg group, and (22.54& #177;8.54)s for the 4.0 mg/kg group; the times of platform crossings were 6.64& #177;0.96 for the control group, 4.23& #177;1.04 for the 2.0 mg/kg group, and 3.19& #177;1.11 for the 4.0 mg/kg group. The ultramicroscopic observation showed the damages to neuron synaptic structure in hippocampus was positively correlated with the exposure dose of nicotine.
Conclusion Maternal exposure to high-dose nicotine during pregnancy would affect offspring rat's growth and development, especially the abilities of early reflex, space learning and memory. A potential mechanism could be the damage to nerve growth and development induced by nicotine.
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