Periadolescent oral manganese exposure affects conditioned place preference by cocaine and conditioned place aversion by lithium chloride in rats

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Date

2013-02-22

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Publisher

Texas A&M University

Abstract

Manganese neurotoxicity compromises basal ganglia functions that could affect the limbic system and drug sensitivity. Male rats were orally exposed to manganese chloride (0, 100, 200 mg/kg/day Mn) for 15 days starting at postnatal day (PND) 28. In Experiment 1, conditioned place preference (CPP) was conducted in a two-compartment apparatus in which cocaine was paired with the least-preferred compartment as determined by a pretest. Animals received 0, 2.5, or 5 mg/kg cocaine HCl (i.p.) for 4 days and, alternatively, vehicle-only for 4 days. Animals exposed to 0 mg/kg/day Mn showed an increased place preference for 2.5 mg/kg cocaine and a reduced place preference for 5 mg/kg cocaine. In contrast, animals exposed to 100 mg/kg/day Mn showed an increased place preference for both 2.5 and 5 mg/kg cocaine, and animals exposed to 200 mg/kg/day Mn showed an increased place preference for 5 mg/kg cocaine only. To determine the possible effects of alterations of learning mechanisms by manganese, a conditioned place aversion (CPA) procedure was employed for Experiment 2. Animals received 40 mg/kg lithium chloride (i.p.) for 4 days, and alternatively, vehicle-only for 4 days. Animals exposed to 100 mg/kg/day Mn and 200 mg/kg/day Mn showed an increased place aversion for 40 mg/kg LiCl when compared to animals exposed to 0 mg/kg/day Mn. However, the increase was not statistically significant. These findings are discussed within a framework of possible manganese-induced disturbance of neurochemical function relating to drug reward and learning.

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Includes bibliographical references (leaves 25-27).

Keywords

psychology and biochemistry., Major psychology and biochemistry.

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