THE present study was designed to investigate the effects of infusions into reticular nucleus of thalamus (NRT) or intracerebroventricular (i.c.v.) infusions of muscarinic M1and M2receptor subtype selective drugs on thalamocortically generated neocortical high voltage spindles (HVSs) in awake immobile rats. NRT administration of 2.0 and 20.0 μg McN-A-343, a muscarinic M1agonist, and 20.0 μg methoctramine, a muscarinic M2antagonist, suppressed HVSs. The results suggest that the blockade of presynaptic M2receptors and activation of post-synaptic M1receptors in the NRT suppress thalamo-cortical oscillations and increase neocortical electrical arousal.