Effect of naloxone on aluminum-induced learning and memory impairment in rats

BACKGROUND: Uptake of aluminum may disturb the learning and memory of humans or animals. Naloxone (NAL) has been shown to exert beneficial effects on memory deficits.
AIMS: We investigated the effects of naloxone on aluminum-induced learning and memory impairment in rats.
SETTINGS AND DESIGN: Aluminum-induced learning and memory impairment model was established by gavage of Aluminum chloride (600 mg/kg) for 3 months. Rats were divided into three groups viz. naloxone-treated rats (NAL 0.8 mg/kg, i.p. daily for 7 days), non-treated model rats and normal controls.
MATERIALS AND METHODS: The Morris water maze test was performed to study spatial learning and memory. Long-term potentiation (LTP) of the Schaffer collateral-CA1 synapse was recorded. Aluminum and zinc contents in the hippocampus were assayed with atomic absorption spectrophotometry.
STATISTICAL ANALYSIS: Parameters of the hidden and visible platform trials and data of LTP were analyzed using two-way repeated measures ANOVA.
RESULTS: In the hidden platform trials, escape latencies of the NAL rats were significantly shorter than that of the non-treated rats (P=0.000, 95% confidential interval low bound 14.31, upper bound 22.68). In probe trails, the number of entries in the target area of the NAL rats (6.75±1.28 times/min) was more than that of non-treated model rats (4.56±2.16 times/min, P=0.004, 95% confidence interval low bound -3.65, upper bound -0.788). The magnitudes of LTP recorded in the CA1 pyramidal neurons of the NAL-treated rats were significantly augmented when compared to the non-treated model rats (P=0.005, 95% confidence interval low bound 0.16, upper bound 0.84).
CONCLUSIONS: NAL could facilitate spatial learning and memory and enhance LTP in the CA1 region of the hippocampus in aluminum-induced learning and memory impairment in rats.

Keywords
Naloxone, Aluminum, hippocampus, learning and memory, long-term potentiation, Morris water maze