STUDIES ON EEG OF THE NEO-, PALEO-, AND ARCHICORTICES IN ALBINO RAT

抄録

I. Arousal and sleep EEG patterns in rat. The EEG patterns in the neo-, paleo-, and archicortices with their related subcortical nuclei were almost the same as those of cats or rabbits.
FIG. 1 (A) is an example of the arousal pattern in which the amygdala shows low voltage fast waves (ca.30 cps), the hippocampus regular slow waves (4-6 cps), and the frontal cortex low voltage fast waves (ca.40 cps).
FIG. 1 (B) shows the drowsy pattern elicited by intravenous administration of progesterone (15mg/kg), in which irregular slow and fast waves are seen in the hippocampus, marked spindle bursts in the frontal cortex and high voltage synchronized waves in the amygdala. This pattern is closely resemble to the pattern shown in FIG. 2 (B) which occurred after intraperitoneal administration of 5mg/kg pentobarbital (Nembutal).
The administration of larger doses of a central depressant caused moremarked lowering of the electrical activity level of the whole brain. FIG. 1 (C) shows the sleep pattern with slow waves and spikes in all traces after intraperitoneal addition of 40mg/kg progesterone.Spontaneously occurred drowsy and sleep patterns were similar to the pattern elicited artificially by drug administration.
From these findings it may be said that the rat's EEG shows the similarpatterns as observed and classified in the cat's EEG by TOKIZANE (1958) and KAWAMURA (1959).
II. Activation pattern in lower level in rat. The activation pattern in lower level has been defined by IMAMURA and KAWAMURA (1959, 1962) to indicate the peculiar electrical activity which may be ranked between arousal and drowsy states.
In rats, the similar pattern was sometimes produced in the neocortex by reticular stimulation or frequently seen under influences of various kinds of central depressant drugs. Thus, after intraperitoneal administration of 30 mg/kg pentobarbital, reticular stimulation (100 cps, 1msec, 1.0 volt) produced the marked activation pattern in lower level in the neocortex, which was characterized by relatively regular waves (7-10 cps) of high amplitude (FIG. 3. B), and by stronger stimulation (1.5 volt) it was rather suppressed as shown in FIG. 3.(C). In this case, the hippocampal regular slow waves were superimposed with enhanced fast waves, although frequency of the slow waves markedly diminished.