Effects of microbial challenge on sleep in rabbits.

Rabbits challenged with viable Staphylococcus aureus exhibit marked time-dependent changes in sleep patterns. To examine the generality of this observation, we monitored sleep patterns for 24 h before and for 48 h after intravenous inoculation of rabbits with Streptococcus pyogenes, Escherichia coli, or Candida albicans. All three agents produced complex time-dependent changes in sleep. Inoculation with S. pyogenes or C. albicans increased the time spent in slow-wave sleep (SWS) during h 4-20 after challenge. Electroencephalographic delta wave amplitudes (DWA) increased during h 4-8 after injection, but decreased during h 24-38 after inoculation. Altered sleep patterns were not observed when similar doses of heat-killed organisms were administered. In contrast, inoculation with E. coli produced a large increase in both SWS time and DWA for the first 2-4 h after inoculation. DWA then decreased from 6 to 32 h after inoculation. Similar effects occurred when heat-killed E. coli were administered. Rapid eye movement sleep was reduced by all three agents. These data demonstrate that altered sleep patterns occur in response to infectious challenge in rabbits, and that these changes are related to the type of infectious organism involved.