ABSTRACT
Each investigator has been busy isolating and identifying his or her own material, and has been concerned mostly with proving the validity of a single substance and its related compounds. Little attempt has been made to analyze the mutual relationship of the putative sleep substances. Among a number of putative sleep substances, compounds, such as delta-sleep-inducing peptide, uridine, and muramyl peptides (MP) were isolated directly from the body fluids or the cerebral tissues of sleeping or sleepy animals. The time sequence interaction of coexisting, multiple sleep substances is suggested in the case of MP-mediated excess sleep. The sequential i.c.v. infusion of the above two sleep substances resulted in a significant, sequence-dependent change in sleep-waking dynamics, which was quite different from the time-course sleep promotion induced by the single or combined administration of each substance. Thus, the preceding activity of a sleep substance during the latest phase of rest and the early phase of activity in rats brought about differential changes.
