Presynaptic NMDA Receptors

NMDARs can be found on dendritic spines and many other locations. Postsynaptic locations are logical given that presynaptic neurons release glutamate. However, they can also be found on or near presynaptic terminals (boutons). In this case they can act as "autoreceptors" that provide direct feedback to the presynaptic terminal and, possibly, indirect feedback to the soma.

In a paper by McGuinness et al, 2010, the authors reported that preNMDARs allow more Ca2+ to enter the presynaptic terminal, elevate [Ca2+]_i, and increase the probability of vesicle release during an action potential.

McGuinness, L, Taylor, C, Taylor, RDT, Yau, C, Langenhan, T, Hart, ML, Christian, H, Tynan, PW, Donnelly, P, and Emptage, NJ (2010). Presynaptic NMDARs in the hippocampus facilitate transmitter release at theta frequency. Neuron, 68(6):1109-27.