Barbara Sorg’s formaldehyde animal model has shown that exposure to the chemical increases levels of stress-hormone production.

For those who suffer from multiple chemical sensitivity, or MCS, a trip to the grocery store may be all it takes to bring on severe headaches, joint pain, muscle fatigue, dizziness, or difficulty in thinking. Barbara Sorg, professor, Veterinary and Comparative Anatomy, Pharmacology, and Physiology at Washington State University, would like to help change that.

MCS, along with panic disorder, post-traumatic stress syndrome, and other similar illnesses, is little understood. All appear to be initiated by an event such as chemical exposure, trauma, or illness. With MCS, it may be one large exposure, such as from a chemical spill, or repeated low-level exposures, such as from home pesticide spraying.

Current research suggests that in susceptible individuals, these events can cause a memory trace to be created in the brain that connects the chemical initiator and the symptoms of the disease. Once created, the memory trace can be activated not just by the original chemical, but also by other chemicals.

It is obviously difficult, if not impossible, to directly study the development of pathways in the human brain. Scientists such as Sorg usually use relevant animal models for this type of work. Sorg has spent the past eight years developing and studying a model in which exposure to formaldehyde is used to examine stress responses and conditioned fear in rats.

Increased levels of stress hormones are thought to lead to changes in the brain, some of them in areas where the brain pathways thought to be responsible for MCS occur. Conditioned fear is believed to be a relevant model for posttraumatic stress and panic disorders. It involves linking an odor or other sensory input with an unpleasant occurrence. When conditioning occurs, the sensory input alone will cause the response appropriate to the unpleasant occurrence.

Sorg’s formaldehyde animal model has shown that exposure to formaldehyde makes rats more sensitive to odors in tests of conditioned fear. It also has shown that exposure to formaldehyde increases the animals’ everyday or basal levels of stress-hormone production.

Currently, Sorg is using her formaldehyde research as a basis for developing a pesticide model that can be used to determine how low-level pesticide exposure may alter the ability of the brain to link pesticide exposure and the symptoms of panic. The pesticide is Lindane, a common treatment for head lice. Other scientific research has suggested that Lindane causes higher-than-normal levels of anxiety, and Sorg sees it as a good means of moving into the study of pesticides and developing a model that can be used to test other pesticides. Her initial work with Lindane indicates that there is a difference between untreated and treated animals, the latter showing a conditioned fear response lasting up to five weeks longer than that of the untreated animals.

A great deal more work will be done in order to test and refine Sorg’s new model. Her goals include determining what changes in the brain are associated with the production of the conditioned fear response in treated animals. More important, for those who suffer from MCS or may develop it in the future, she will be able to use the system to test treatments that will prevent the development of the disorder or block the symptoms in those who already have it.