The competitive NMDA receptor antagonist CPPene stimulates NREM sleep and eating in rats

Systemic administration of noncompetitive NMDA receptor antagonists, such as MK-801, produces a period of intoxication followed by non- rapid eye movement (NREM) sleep with greatly elevated delta EEG activity. We have hypothesized that the delayed NREM delta EEG increase is a homeostatic response to the immediate elevated limbic metabolism that these drugs produce. Here we test this hypothesis by examining the sleep and EEG effects of CPPene, a competitive NMDA antagonist that does not elevate limbic metabolism. We recorded EEG in seven rats following mid-dark period systemic injections of saline and three doses of CPPene. CPPene did not produce the delayed NREM delta increase. Instead, CPPene increased eating time and dose dependently increased NREM sleep duration shortly after injection. These differences in sleep EEG response to a competitive versus the noncompetitive NMDA antagonists are consistent with the possibility that the increased NREM delta following noncompetitive antagonists is a homeostatic response to increased limbic metabolism.