7.
Speculative diagram of two possible mechanisms for nicotinic EPSP reduction requiring NMDAR activity. A, Presynaptic nAChR are located selectively at synapses lacking postsynaptic AMPAR (lower panel). nAChR activation leads to reduction of transmitter release, denoted by (-). Modified from Metherate and Hsieh, 2004. B, nAChR are located postsynaptically at mixed AMPAR/NMDAR synapses. nAChR activation leads to NMDAR-dependent signaling via a retrograde message (dashed line) that reduces presynaptic transmitter release.