Neurotoxic effect of lead at low concentrations

The effects of lead exposure at low concentrations were evaluated by studyi ng the post-rotatory nystagmus (PRN) in two groups of rats exposed for 3 mo nths to 50 parts per million (ppm) of sodium acetate and 50 ppm of lead ace tate, respectively, in the drinking water. Only animals treated with lead a cetate showed changes of the PRN parameters which were significantly relate d to the concentration of lead in the blood and in brain structures. The pa tterns of PRN responses were characterized and classified into four types; progressively inhibitory (40%), prematurely inhibitory (25%), late inhibito ry (25%), and excitatory-inhibitory (10%). No alterations of the PRN parame ters were observed in the animals treated with sodium acetate. The results show that exposure to lead, even at low concentrations, impairs both sensor y and motor functions. The findings also point out that the vestibular syst em and brain stem structures which generate and control the PRN represent t argets of the action of this heavy metal. Finally, the results indicate tha t the evaluation of the vestibulo-ocular-reflex can provide a test suited f or the screening of the neurotoxic effects of lead even in the absence of c linical signs typical of lead intoxication. (C) 2001 Elsevier Science Inc.