Neuropeptide Y does not alter NMDA conductances in CA3 pyramidal neurons: a slice-patch study.

Neuropeptide Y (NPY) has been reported to inhibit excitatory neurotransmission in hippocampus presynaptically. Recently, it has been suggested that NPY also potentiates N-methyl-D-aspartate (NMDA)-mediated excitatory responses in hippocampus, by action at a sigma or phencyclidine (PCP) binding site. We tested this hypothesis by examining the action of NPY on CA3 pyramidal cells using slice-patch voltage clamp recordings. NPY did not affect inward currents elicited by iontophoresis of NMDA onto the proximal dendrites of these cells under two different conditions, but did reduce the excitatory postsynaptic currents elicited by mossy fiber stimulation. NPY therefore does not appear to directly alter the postsynaptic NMDA response in CA3 cells.