Signs of synchronized sleep elicited by local application of leptazol to a circumscribed area of the ventral surface of medulla oblongata in the cat.

Topical application of some drugs to the ventral surface of medulla oblongata has been found to cause changes in blood pressure and respiration and release of vasopressin. In the present investigation, electrophysiological changes induced in the electrocorticogram of cats by drugs applied to this area of the central nervous system were studied. In eight animals kept anesthetized with sodium pentobarbiturate, leptazol (200 mg/ml) was applied bilaterally (20 microliter on each side) to a small area of the rostral portion of medulla oblongata while blood pressure, respiration, the electrocorticogram from the sigmoid gyri, the nictitating membrane and the pupil width were monitored. In some preparations sodium pentobarbiturate was also applied to the same area after leptazol. Within 30 s of leptazol application to the surface, active spindling started in the sigmoid gyri, simultaneously with myosis, relaxation of the nictitating membrane and inhibition of the limb retraction in response to noxious stimulation. All these changes characterize the state of synchronized sleep. Topical application of pentobarbital to the same area suppressed spindling and reversed the other signs of synchronized sleep. The possible intervention of some known hodological systems or of the sleeping factors described by some authors in the genesis of the above phenomena is discussed.