In vivo exposure to lead does not influence muscarinic receptors in the frontal cortex of the mouse brain

Abstract

The effects of lead on muscarinic receptors in the brain of adult and juvenile mice were studied in vivo. Lead was administered for periods of 10, 30, and 90 days to adult mice. Perinatal exposure was achieved by treating gestating mice from the day of conception. The exposure was continued after birth and during weaning until 30 days postnatal. Both groups, adult mice and pups or their mothers were given a solution of 10, 100, and 1000 ppm inorganic lead in their drinking water, which was available ad libitum. Radioligand binding studies were performed in vitro to determine receptor densities ( B max) and affinities ( K D values) in brain membranes of the frontal cortex. In addition, the binding of a selective muscarinic agonist and of an antagonist to receptor subtypes was investigated. Inhibition curves of 3H-quinuclidinylbenzilate ( 3H-QNB) labelled membranes were determined with the m 1-antagonist pirenzepine and the m 2-agonist carbachol to distinguish between high- and low-affinity agonist and antagonist states in the cortex. Few important changes in density or affinity to the membrane receptors investigated were seen in animals treated with lead. Similarly the properties of high- and low-affinity muscarinic receptor binding were unchanged in the groups exposed to lead. In conclusion, the present results show that lead does not affect the muscarinic receptors in mouse brain under the experimental conditions used.