Pharmacology of evoked cholinergic synaptic responses. A, Electrical stimulation of the Layer 6–white matter boundary elicited small synaptic currents that were reversibly reduced by the nicotinic antagonist DHβE (100 μm). Recordings in A were obtained from a P23 pyramidal cell (B) in the presence of 20 μmd-APV, 50 μm CNQX, and 50 μm picrotoxin (PTX). Eachtrace in A represents the average of 14–20 traces. The small peaks occurring with a longer latency than the initial response may represent activation of a different set of fibers or spontaneous synaptic activity.