Rats were exposed to trichloroethylene (TCE) vapour for about five five-day weeks at concentrations from 100 to 1 000 ppm, and at 100 ppm for 12 1/2 weeks. The social behaviour of paired male rats was observed periodically in the home cage for five minutes after they had been exposed to TCE. The principal finding was a consistent reduction of up to 24% in the total acitivity. A single day's exposure to TCE was sufficient at the highest concentration. At 100 ppm, a similar decline in activity was significant after 1 1/2 weeks' exposure in one experiment and 8 1/2 weeks' in another. The decline in activity was fairly uniform and not usually because of specific reductions in particular kinds of behaviour. However, exploration of the cage and submission to, or escape from, the other rat were sometimes specifically reduced. In an 'exploration-thirst' test, rats were deprived of water overnight and placed on two or three occasions in a previously unfamiliar cage. Rats exposed to 100, 200, or 1 000 ppm TCE found water and began drinking sooner than their controls without altering the rate of movement about the cage. These results suggest lowered performance in a familiar situation where rats are usually very active and some loss of inhibitory control in an unfamiliar one. At the present threshold limit value, repeated exposure to TCE eventually had effects similar to those of one day's exposure to a higher concentration, but only after a widely variable delay.

Aggression↗

PubMedDate not supplied

An ethologist's approach to behavioural toxicology.

Ethology, the biology of behaviour, is briefly introduced, and a review is presented of two ethological methods applied to toxicology. (1) When elements in the behaviour of rats in a social situation are objectively observed, chemically-induced changes in several kinds of behaviour can be detected at low doses. Changes are specific and repeatable in long-term experiments. Effects of nicotine at a 'smoking' dose, or trichloroethylene at the Threshold Limit Value, were reversible; limited tolerance developed to methyl mercury dicyandiamide. (2) An 'Exploration-Thirst' method is simple enough for use as a screen. It was compared with conventional toxicological methods for 30 compounds in routine screening (20 acute intraperitoneal, 10 subacute inhalation). Both ethological methods are sensitive enough to estimate 'no-effect' doses. They also distinguish non-specific toxic effects (consistent with the animal's equivalent of 'feeling ill') from various more specific CNS effects comparable to those of human experience.

Animals↗