Selective effect of malathion on blood coagulation versus locomotor activity.

The objective of this study was to compare the neurotoxic effects of acute malathion exposure with the potential blood coagulation effects. We administered various doses of malathion to Wistar rats by i.p. injection, and then we assessed the effects on blood coagulation screening tests and activity in the open field locomotor test. The activated partial thromboplastin time (APTT), but not the prothrombin time (PT), was significantly prolonged by up to 6.6 seconds (38% of the preinjection value) after the administration of malathion (3-75 mg/kg; 1-25% of the LD50). This effect was observed 5 minutes after injection and persisted for at least 3 hours. In contrast, no effect was observed on the general locomotor activity, movement, rearing, or stereotopy during 3 hours after the i.p. administration of the same doses of malathion. Our data indicate that malathion affects blood clotting before the nervous system (locomotor) function.