Lead exposure can hinder recovery from a brain injury

Oct 25 2004

Lead exposure at a young age can hurt the brain's development and cause learning and behavioral problems. It may also interfere with recovery from a brain injury.

A new study by scientists at Jefferson Medical College shows that young rats exposed to low levels of lead take significantly longer to recover from a brain injury than those animals that weren't lead-exposed.

According to Jay Schneider, Ph.D., professor of pathology, anatomy and cell biology at Jefferson Medical College of Thomas Jefferson University in Philadelphia, even low levels of lead exposure can have profound effects on the structure and function of the developing nervous system and cause attention, memory, learning, emotional and other behavioral problems that persist into adulthood.

Dr. Schneider says that it isn't uncommon for children to have brain injuries. At the same time, the young brain is extremely "plastic," and has a tremendous capacity to try to repair itself and recover. Yet, no one has looked at the effects of lead exposure early in life on the response of the brain to a later injury.

In an experiment, Dr. Schneider and his co-workers injured a specific part of the rat's brain that controls the hind limbs in two groups of animals: one that had been exposed to lead and one that had not. They found that while there was some recovery of function in both groups, the lead-exposed rats did not recover as much or as quickly as did the unexposed animals.

Dr. Schneider presents his group's findings Oct. 25, 2004, at the Society for Neuroscience's annual meeting in San Diego.

In one test, they compared the animals' abilities to walk across a narrow beam. Normally, rats can navigate the beam with few mistakes, he says.

"When we create the brain damage, initially, all of the animals make errors," he says. "The control animals very quickly recover and make far fewer mistakes in the next week. The lead-poisoned animals take longer to improve, and improve much less.

"These results potentially add one more item to the long list of reasons why preventing lead exposure early in life is so important," he says.

Next, the researchers want to examine the effects of lead poisoning on recovery from brain injury over a longer period of time. One question, says Dr. Schneider, is whether or not lead-poisoned animals eventually recover to the same degree as the unexposed animals. They also plan to try to determine if there is a threshold for lead exposure and its effects of the brain's ability to recover following a brain injury.