Abstract:
Biometals play a large role within the human body where a deviation from normal levels
can result in behavioral abnormalities. Copper (Cu) is a transition metal with
physiological importance and has been shown to have a remediating effect on the
behavioral impairments caused by excess Zinc (Zn). In order to examine the effects of a
Cu deficient diet directly, diets mildly deficient in Cu with identical Zn levels were
developed and resulting behavioral effects were examined. Forty-five male Sprague-
Dawley rats were tested for cued fear learning, fear extinction, and motor functioning in
order to assess the effect of dietary metal content on behavior. Using specially formulated
diets, a mild Cu deficiency was examined directly, as opposed to a Cu deficiency attained
through excess levels of Zn. Animals were given a Cu deficient diet (4ppm Cu) while still
in prenatal development, a Cu deficient diet (4ppm) after birth (postnatal), and a Cu
control diet (16ppm) after birth (postnatal) and were raised for a period of 4 months.
Throughout the fear learning and extinction paradigm, there were no significant differences between the dietary conditions except on the second day of fear extinction
recall where a marginally significant difference was detected with the prenatal Cu
deficient group exhibiting higher percent freezing than the postnatal Cu deficient and
control groups. However, in analysis of the accelerating rotarod task, significant
differences between the diets were found on days 2 and 3 as well as when the
performance was averaged across all three days of testing and across the nine total trials.
The postnatal Cu deficient group consistently exhibited lower latencies to fall. Significant
differences were noted in the weights between the dietary groups. At weaning (PND 21),
the prenatal Cu deficient weighed significantly more than the postnatal Cu deficient, and
at 4 months of age, the postnatal Cu control group weighed significantly more than the
pre- and postnatal Cu deficient groups. These results suggest that a diet mildly deficient
in Cu may lead to motor abnormalities and impairment and not necessarily lead to
significant differences in fear learning. These data show the important role that dietary
metal content plays in behavior and that using appropriate control and experimental diets
can have a significant effect on rodent behavioral experiments.
