Spontaneous open-field behavior in thiamin-deficient rats.

Open-field testing has proven useful for evaluation of the effects of drugs on behavior. We now present detailed methods for subdividing open-field behaviors into four categories: sniffing, grooming, resting, and staring. Upon initial exposure to the open field, sniffing is the predominant behavior. With habituation, sniffing and grooming decrease, and resting and staring increase. Treatment with a thiamin-deficient diet and pyrithiamin, a centrally acting thiamin antagonist, markedly increases staring behavior by day 3 of treatment. Animals that are treated with a thiamin-deficient diet and oxythiamin, a peripherally acting thiamine antagonist, do not have increased staring behavior. Therefore, increased staring behavior is an early behavioral change in central nervous system thiamin deficiency. Staring and other spontaneous open-field behaviors may be useful variables to monitor in thiamin deficiency and in other metabolic encephalopathies.