The aim of this paper was to study the effects of microinjections of carbachol, a mixed cholinergic agonist, into the nucleus basalis of Meynert (NBM) of rats on the wake-sleep cycle. Carbachol (2.74 nmol) was able to increase wakefulness (W) and decrease desynchronized sleep (DS). To verify the hypothesis that the effects of carbachol are at least partially mediated by the glutamatergic system, the NMDA antagonist 2-amino-5-phosphonopentanoic acid and the non-NMDA antagonist D-gamma-glutamylaminomethanesulfonic acid were injected into the NBM before carbachol. Pretreatment with these glutamate receptor antagonists counteracted the effect of carbachol on DS. The effect of carbachol on W was not modified by the pretreatment with the glutamate receptor antagonists. This is the first study showing that carbachol injected into the NBM increases W and decreases spontaneous DS in the rat. Moreover, our results tend to indicate that the decrease in DS following the injection of carbachol into the NBM is related to the release of endogenous glutamate.