Convulsive Seizures in Dieldrin Exposed Sheep during Photic Stimulation

Dieldrin, a chlorinated hydrocarbon insecticide, causes hypersensitivity and muscular fasciculations which may be followed by clonic-tonic conv~~lsive seizures. There are changes in the cortical electroencephalogram (EEG) which occur prior to clinical toxicity. These changes consist of high amplitude (200 to 300 pv), slow wave (4 to 5 Hz) spindles of 1 to 3 sec. duration (Van Gelder, et al., 1968). As exposure continues, the slow wave activity occurs more frequently and is of greater duration. The signs of clinical toxicity described above are usually evident at this time. During convulsive seizures, the EEG consists of high-amplitude, fast waves with some spike-wave complexes similar to those seen in petit ma1 epileptic seizures. The EEG record gives an indication of the imminence of convulsive seizures. The presentation of a high intensity, variable-frequency light (Grass Model PS-2 Photo Stimulator) precipitated convulsive seizures in 3 exposed sheep prior to the occurrence of clinical toxicity. These same animals were unaffected by the photic stimulation prior to exposure. At approximately 11 to 14 Hz the animals began to convulse and continued convulsing as long as the photic stimulation was present. The convulsive seizure ended with the termination of the strobe. Unexposed control animals remained unaffected by this photic stimulation. It is not known whether the precipitation of convulsive seizures is unique to visual stimulation or is a more general response to massive sensory input. Further investigation with the use of repetitive auditory stimulation is underway. REFERENCE

Anesthesia · Audiology · Electroencephalography · Fasciculation · Photic Stimulation · Sensory stimulation therapy · Spike-and-wave · Stimulation · Toxicity · Visual perception · Electrochemical Analysis and Applications · Internal Medicine · Medicine · Neuroscience · Psychology