Fig. 3. Role of α⁷subunit–containing nicotinic receptors in ketamine responses. α Bungarotoxin (αBgTx), a selective antagonist of nicotinic receptors containing the α⁷subunit, did not alter the nicotine-evoked inward current (A ) or increase in miniature glutamatergic synaptic event (mini) amplitude (B ), but did block the nicotine-evoked alteration in mini frequency (C ). These results are consistent with the findings that nicotinic receptors containing α⁷subunits are predominantly located presynaptically and alter the probability of transmitter release. Inclusion of ketamine in the perfusate continued to inhibit the nicotine-evoked inward current (D ), but the effect of ketamine on the nicotine-evoked increase in mini frequency was occluded by the presence of αBgTx (F ). Neither ketamine nor αBgTx had an effect on mini amplitude (E ).