A naturally occurring delta-EEG enhancing nonapeptide in rabbits

By extracorporeal dialysis of blood from the sagittal venous sinus in rabbit donors during electrical stimulation of the ventromedial intralaminary thalamus, a hemodialysate was obtained. This dialysate, or its purified fractions, infused into the mesodiencephalic ventricular system of recipient rabbits, induced behavioral and electroencephalographic (EEG) changes, i.e., enhanced delta-EEG. These effects of the dialysate and of its subsequent fractions were quantified by EEG analysis of the cortical delta activity (2–3 Hz), using a calibrated automatic wave analyzer. The activity values of the last pure fractions were furthermore processed on an 1108 computer system. It was thus possible to express the delta enhancement in RMS μV and the corresponding time integral referred to the preinfusion values as well as to the values of the control rabbits.