Fenvalerate-induced alterations in circulatory thyroid hormones and calcium stores in rat brain.

Intraperitoneal administration of fenvalerate, a synthetic pyrethroid, in male rats for 45 days in doses of 100 and 200 mg/kg body weight/day induced hyperexcitability, tremors and paralysis. Tremors were observed after 7 days and gradually reached maxima on 45th day. The symptoms were more marked in rats treated with 200 mg/kg body weight/day. Fenvalerate provoked significant elevation of circulatory thyroid hormones, namely tri-iodothyronine (T3) and thyroxine (T4). A significant increase in total calcium as well as protein-bound calcium in whole brain and hypothalamus were recorded. The elevation of circulatory thyroid hormones as well as the active calcium pool could be together responsible for impairment of motor activity by altering various neuronal processes.