In all 22 cases, quiescent periods disappeared Venetoclax mouse during wakefulness (Figures 3C and 3D). Wakefulness still abolished quiescent states in L4 neurons following L6 lesions directly below the barrel, which disrupt both L6 and VPM input (n = 2; data not shown). Thus, afferent thalamic input is not the mechanism that produces the awake state of cortical neurons. We initially suspected that release of the neuromodulator acetylcholine (ACh) in the cortex was responsible for the switch in cortical dynamics. Electrical stimulation of cholinergic nuclei in anesthetized animals

is well known to simulate awake-like EEG, local field potential, and cortical Vm, effects that are blocked by antagonists of muscarinic ACh receptors (Goard and Dan, 2009, Metherate et al., 1992 and Steriade et al., 1993a). If the awake state indeed depended on ACh, blocking muscarinic receptors should also induce synaptic quiescence during wakefulness. Systemic injections of the muscarinic antagonist scopolamine, applied in even higher doses

than in previous studies (5 mg/kg IV or IP), failed to induce quiescent states in L4 neurons of awake rats (Figure S4A). selleck screening library To ensure that antagonists reached their targets, we recorded from L4 neurons while locally perfusing 1 mM muscarinic (atropine) and nicotinic (mecamylamine) antagonists from a pipette whose tip was positioned 50–75 μm from the patch pipette tip. In each case, ACh blockers did not affect awake Vm (Figures S4B and S4C). Although arousal-induced changes were independent of thalamic afferents, thalamocortical input and ACh could conceivably interact to alter cortical dynamics. We therefore combined local perfusion of blockers with somatotopically others aligned

thalamic lesions (Figure 4A), which render a L4 barrel a relatively isolated network (see Discussion). In every recording following thalamic lesion (n = 8), perfusing 100 μM–1 mM atropine and mecamylamine failed to prevent awake patterns of synaptic inputs (Figures 4A and 5E, black). Inclusion of an α7 nicotinic antagonist (methyllycaconitine) similarly had no effect on awake Vm (n = 3; data not shown). Thus, 18 out of 18 cholinergic blocker experiments yielded negative results, in which wakefulness continued to abolish synaptic quiescence. Effective delivery of blockers was verified by a positive control. ACh enhances contrast sensitivity of L4 neurons in macaque visual cortex via nicotinic receptors on thalamocortical terminals (Disney et al., 2007), which similarly exist in rodent somatosensory cortex (Gil et al., 1997). Cholinergic blockade should therefore shift the sensitivity of L4 neurons to the velocity of whisker movements, the tactile analog of visual contrast. The time course of L4 integration should also differ due to muscarinic receptors on corticocortical terminals (Eggermann and Feldmeyer, 2009 and Kruglikov and Rudy, 2008).