Maternal zinc supplementation improves spatial memory in rat pups

Abstract

A large body of evidence supports an opinion that adequate dietary zinc is essential for prenatal and postnatal brain development. Behavioural effects of maternal supplementation with ZnSO(4) were analysed in rat pups with the Morris water task performance, a hole board and a T-maze. Wistar females during pregnancy and lactation received a drinking water solution of ZnSO(4) at doses of 16 mg/kg (group Zn16) or 32 mg/kg (group Zn32). Behavioural tests were conducted on the 4-week-old male rat pups. Zinc concentration in the serum, hippocampus and prefrontal cortex of offsprings was determined by means of atomic absorption techniques. The Newman-Keuls multiple comparison test revealed an increase of climbing in the Zn16 group in comparison to the control group (Con) and the Zn32 group during the hole board test. ANOVA for repeated measures showed a significant memory improvement in both supplemented groups compared to the control in the probe trial on day 5 of the water maze test. ZnSO(4) treatment significantly elevated zinc levels in the rat serum. Follow-up data on brain content of zinc in the hippocampus revealed significant differences between the groups and in supplemented groups correlated with crossings above the original platform position. These findings suggest that pre- and postnatal zinc supplementation may improve cognitive development in rats.

Fig. 1

Scheme of maternal pre- and postnatal zinc treatment and sequence of behavioural tests (Con, n = 10; Zn16, n = 8; Zn32, n = 8)

Fig. 2

Escape latency (±S.E.) during acquisition of the spatial navigation task (16 trials) for the control (n = 10) and rats pre- and postnatally supplemented with ZnSO₄ (Zn16, n = 8; Zn32, n = 8)

Fig. 3

Spatial probe data from the platform area crossings for the control and ZnSO₄-treated rats in the water maze task on day 5 (trial 17). The test was run in the same manner as the acquisition trials, except that the target was absent and the trial was terminated after 60 s. The measure given is platform crossings ± S.E.: the number of times the rat passed through a nominal area defining the originally correct platform position. ^** p < 0.01, Zn16 vs control; •p < 0.05, Zn32 vs control (Newman–Keuls test)

Fig. 4

The percentage of time spent in quadrants for the control (n = 10) and ZnSO₄ (Zn16, n = 8; Zn32, n = 8)-treated rats in the water maze task on day 5 (trial 17). The test was run in the same manner as the acquisition trials, except that the target was absent and the trial was terminated after 60 s. **p < 0.001, Zn16 and Zn32 vs control; *p < 0.05, Zn16 vs control; ••p < 0.01, Zn16 vs Zn32 (Newman–Keuls test)

Fig. 5

Mean number of climbings (±S.E.) during hole board for the control and rats pre- and postnatally supplemented with ZnSO₄. **p < 0.01, Zn16 vs control; ••p < 0.01, Zn32 vs Zn16 (Newman–Keuls test)

Fig. 6

T-maze spontaneous alternation (±S.E.) average of all trials. *p < 0.05, Zn16 vs control; ••p < 0.01, Zn32 vs Zn16 (Newman–Keuls test)