Effect of Strychnine on the Electroencephalogram Recorded from the Wulst of Curarized Adult Chickens

Abstract

The influence of strychnine on the Wulst EEG has been studied in 32 curarized adult hens. Large spontaneous spikes (1–4 mV.) were found to be elicited by an intravenous injection of strychnine nitrate at doses of 2 to 5 mg./kg. body weight on the adult chicken telencephalon (the Wulst), as well as local application of 0.2–2.0% strychnine into the cerebral hemisphere. One mg./kg. strychnine intravenously injected induced a short lasting seizure-like discharge which was followed by a train of spiky waves (below 1 mV.) in 5 out of 11 hens, and injected subcutaneously induced low voltage and fairly rhythmic fast waves (16–18 c.p.s.; 20–50μV.) several minutes after administration. An effective intravenous dose of 0.5 mg./kg. strychnine produced low voltage and fairly rhythmic fast waves, but no spikes were observed. The waveform and the amplitude of the spikes induced by either an intravenous or a local injection of higher doses of strychnine were not different. The spikes were generally biphasic with a negative surface wave followed by a positive surface wave. The results obtained suggest that a threshold occurs electroencephalographically with spikes shown at a large intravenous dose of 1 mg./kg. strychnine nitrate, and that very large intravenous doses of 2 to 5 mg./kg. strychnine could penetrate the blood-brain barrier in the adult chicken brain.