Abstract

Thiopental, 2 mg/kg, and DMHP, 0.2 mg/kg, increased the threshold for EEG arousal in acute preparations, and for behavioral, as well as EEG, arousal in chronic preparations. Arousal was induced in all preparations by electrical stimulation of the reticular formation.

It is suggested that some responses following thiopental, such as cortical desynchronization from the drug and synchrony instead of asynchrony during stimulation, as well as occasional initial lowering of threshold for arousal by both thiopental and DMHP, may be explained on the basis of an ascending inhibitory reticular system.

An attempt to produce EEG and behavioral arousal by the selective circulation of thiopental to the pontomedullary region in chronically prepared animals was successful in only 2 of 8 preparations.

Thiopental, 5 to 10 mg/kg, and DMHP, 0.2 mg/kg, had no effect on the recruiting response.