Elevated cerebellar cyclic GMP levels during the deltamethrin-induced motor syndrome

Adult male Porton albino rats received deltamethrin (0.5--40.0 mg/kg IP) or glycerol formal solvent IP. Their behaviour was observed during the subsequent 110 minutes and the incidence and latency of salivation, tremor and incoordination and spontaneous choreiform episodes were noted. Cyclic GMP levels in the cerebellum were determined by radioimmunoassay at various times after deltamethrin administration. The development of the motor syndrome was dose-dependent and followed a specific time course. The threshold dose for profuse salivation and tremor and incoordination was 2.5 mg/kg IP, and for spontaneous choreiform episodes, 5.0 mg/kg IP. The latency of tremor and incoordination decreased significantly as the deltamethrin dose was increased. The first significant increase in cyclic GMP levels in the cerebellum was at 70 minutes, which was 10 minutes after the mean latency of tremor and incoordination. The levels increased further at 100 minutes which was approximately 20 minutes after the mean latency of spontaneous choreiform episodes. Deltamethrin did not have a dose-dependent effect on cyclic GMP levels. The results suggest that deltamethrin changes cerebellar cyclic GMP levels indirectly.