Toxicity of Bis (tri-n-butyltin) oxide on Learning and Development in the Rat

The toxicity of his (tri-n-butyltin) oxide (TBTO) was studied in THA rats. Doses of 0 (control), 10 or 15mg/kg/day of TBTO were administered to adult rats for 12 consecutive days, and 0, 5 or 10mg/kg/day was given to pregnant rats from day 6 to day 20 of gestation by gastric intubation. In the adult rat exposure experiment, the 15mg/kg group showed slightly decreased body weight and spontaneous motor activity, and a low avoidance rate in the Sidman avoidance test in the early stage of administration. In the pregnant-rat exposure experiment, no effect of TBTO was seen in either the 5mg/kg or 10mg/kg groups in dams while all pups in the 10mg/kg group died by postnatal day 3. Little effect of TBTO on body weight, pinna detachment, incisor eruption, eye opening, surface righting, cliff avoidance, pivoting, negative geotaxis and auditory startle was found in the 5mg/kg pups. In the Sidman avoidance test, the avoidance rate of the 5mg/kg pups was lower than that of control pups in the early stage of the session. In a water E-maze test, the swimming time to the goal and the number of errors were increased in the 5mg/kg pups. In a reversal water E-maze test, increases of the swimming time to the goal and the number of errors made by the 5mg/kg pups were marked. These results suggest that TBTO administration disrupts the learning acquisition of rats, and that the toxicity of TBTO is greater in prenatally exposured pups than in adult rats.