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nAChRs are involved in the presynaptic control of dopamine release in the striatum (Hersch et?al., 1994, Marshall et?al., 2002, Rapier et?al., 1990?and?Wonnacott et?al., 2000). To confirm that cholinergic interneuron-driven enhancement of dopamine release is mediated by activation of nAChRs, we monitored dopamine levels while performing selective optical activation of cholinergic interneurons in the absence and presence of nAChR antagonists. Mecamylamine (n?= 6) decreased cholinergic interneuron stimulation-induced dopamine release with a half maximal inhibitory concentration (IC50) of 0.61?��M (Figure?3A). The highest dose used (20?��M) decreased dopamine levels by 85.8 �� 3% compared to pre-drug conditions. In mammals, combinations of nAChR subunits from subfamilies II (��7) and III (��2�C��6, ��2�C��4) result in the formation of functional heteropentamers and homopentamers (Le Nov��re et?al., 2002). In striatal dopamine terminals, heteropentamers display [http://www.selleckchem.com/products/pd-1-pd-l1-inhibitor-2.html selleck] two ��/�� pairs in the form of ��4/��2 and/ or ��6/��2 and/or ��4/��4 (Champtiaux et?al., 2003). Nicotinic control of striatal dopamine [http://en.wikipedia.org/wiki/Thalidomide Thalidomide] release depends on ��2 subunit-containing nAChRs (Zhou et?al., 2001?and?Exley et?al., 2012). To verify the role of ��2-containing receptors in the augmentation of accumbal dopamine release by selective activation of cholinergic interneurons, we examined the effect of the ��2-containing nAChR antagonist dihydro-��-erythroidine (DH��E). Application of DH��E (1?��M) resulted in a potent reduction of dopamine peak levels elicited by optical stimulation (89.05% relative to pretreatment values; p?[http://www.selleckchem.com/products/lee011.html this website] by glutamate and not by ACh (Guzman et?al., 2011). Because of our findings that endogenous cholinergic activity drives dopamine release in a nAChR-dependent fashion, we next examined if this occurred, at least in part, through activation of AMPA receptors. First, we confirmed that stimulation of cholinergic interneurons led to glutamate release. Under whole-cell voltage-clamp, single pulse optical stimulation of cholinergic interneurons evoked a single excitatory postsynaptic potential in medium spiny neurons (Figure?3C). Furthermore, optical train stimulation failed to produce subsequent excitatory postsynaptic potentials following the initial pulse in the trains (5 pulses at 2 or 30?Hz; see Figure S2). Bath application of the AMPA receptor antagonist 2, 3-dihydroxy-6-nitro-7-sulfamoylbenzo (F) quinoxaline (NBQX) (5?��M) attenuated the excitatory postsynaptic potential amplitude to 18.