The Effects of Heavy Metal Exposure on Behaviour

Abstract

Many of the heavy metals are neurotoxic. Our knowledge of this is from clinical evidence where in most cases high level and/or chronic exposure to the metal produces overt signs and symptoms. Recent controversies however, have singled out two metals, mercury and lead, as being particularly hazardous to the nervous system. The important questions that have arisen from this surge of interest are: at what level of exposure do these metals become neurotoxic and what specific effects do they have on the nervous system? This second concern is of greater interest to neuroscientists as it not only covers the question of toxicity, but may also provide us with some insight into how specific behaviour is moderated. We have investigated the effects of inorganic mercury on man using an information processing based battery of tests. Together with the well known motor disturbances, mercury exposure was shown to produce specific short-term memory impairment(Williamson et al,1982). Recent biochemical evidence suggests a reason for this. Injections of both organic and inorganic mercury reduced Na+/K+ ATP’ase levels (Gallagher et al, 1982) in the rat brain in the same manner as did ouabain. Significantly, Gibbs and Ng (1977) showed using ouabain that short-term memory is Na+/K+ pump dependent. We have used the same battery of tests to investigate the effects of lead exposure on adults. The results of this study also will be discussed.