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CHOLINERGIC AND NORADRENERGIC MODULATION OF LONG-TERM EXPLICIT MEMORY ARE ALTERED BY CHRONIC LOW-LEVEL LEAD EXPOSURE. (U915393)
Driscoll, L. L., M. E. Gilbert, AND B. J. Strupp. CHOLINERGIC AND NORADRENERGIC MODULATION OF LONG-TERM EXPLICIT MEMORY ARE ALTERED BY CHRONIC LOW-LEVEL LEAD EXPOSURE. (U915393). 20(3):363, (1998).
Recent evidence suggests that septohippocampal cholinergic activity is suppressed in rats exposed to low levels of lead (Pb). As a result, noradrenergic activity may be elevated due to compensatory sympathetic sprouting. Therefore, the goals of this study were to (a) determine whether long-term explicit memory is altered in Pb-exposed animals, and (b) if so, to relate these changes to alterations in the cholinergic and/or noradrenergic systems. Explicit memory function was assessed in a 12-arm radial maze with varying retention intervals (0, 3, 6, 9 hrs) imposed after 6 of the arms had been traversed. Subsequently, changes in the noradrenergic and cholinergic systems, respectively, were assessed by administering various doses of the alpha-2 antagonist RU 52583 (0, 1, 2, or 5 mg/kg) or the muscarinic antagonist scopolamine (0, 0.01, 0.02, or 0.05 mg/kg) prior to traversal of the first six arms. Recall for the location of the remaining 6 rewards was tested 6 hr later.
Explicit memory function was significantly better in rats chronically exposed to low-level Pb from birth, relative to controls. In addition, the Pb-exposed rats were significantly more sensitive to the memory impairing effects of scopolamine than controls, and exhibited an altered sensitivity to the effect of RU 52583 on long-term memory errors. The Pb-exposed rats were not, however, more sensitive to the effects of the drugs on the speed of choosing arms or attaining food rewards. This pattern of effects suggests that chronic low-level Pb exposure alters cholinergic and noradrenergic activity specifically in regions involved in mnemonic and/or attentional function, changes which are functionally important for long-term explicit memory.
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Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL CENTER FOR ENVIRONMENTAL RESEARCH