O.H.--a strong slow wave sleep inducing factor in tortoise (Emys orbicularis).

The paper would be a contribution to the very complex and not yet clarified field of neurochemistry of slow wave sleep (SWS). The study was performed on 30 tortoises (Emys orbicularis): 20 "donors" and 10 "receivers". The animals were equipped with chronic cannula inserted in the third ventricular space and electrodes for electrographic recording (EEG, EOG, EMG and ECG). The controls consisted in administration into the third ventricle of receivers of 30 microliters of saline or concentrated cerebro-spinal fluid (CSF) extracts from awake donors. The results were negative, i.e. the injected tortoises conserved their waking state indefinitely. The experiments were performed by introduction of 30 microliters of concentrated CSF extracts obtained from asleep donors into the third ventricular space of receivers. All the animals presented the behavioural and electrographic signs of the physiological SWS. The logical conclusion is that in the development of reptilian SWS, an endogenous SWS-inducing factor, which I called "O.H." (orbicularis hormone), was secreted by some hypnogenic structures and discharged in the CSF, with the consequences presented above.