Somnogenic, pyrogenic, and hematologic effects of bacterial peptidoglycan.

Bacterial infections and certain muramyl peptides elicit a variety of pathophysiological effects including increases in body temperature and slow-wave sleep. Bacterial cell wall peptidoglycan is composed of muramyl peptides. To investigate the ability of isolated bacterial cell walls to enhance slow-wave sleep, rabbits were injected intravenously with cell walls isolated from Staphylococcus aureus or with soluble peptidoglycan prepared from Neisseria gonorrhoeae. These injections increased slow-wave sleep, electroencephalographic delta-wave amplitudes, and body temperature, reduced rapid-eye-movement sleep, and induced neutrophilia and lymphopenia. The somnogenic and pyrogenic effects of S. aureus cell walls developed within 1 h and persisted throughout the recording period. Injections of N. gonorrhoeae peptidoglycan induced similar effects but of larger magnitude and shorter duration. We conclude that peptidoglycan is a bacterial component that mediates the increased sleep observed during infectious disease.