Journal of Neuroscience, Vol 16, 1422-1429, Copyright © 1996 by Society for Neuroscience
Neuropeptide Y1 receptors inhibit N-type calcium currents and reduce transient calcium increases in rat dentate granule cells
AR McQuiston, JJ Petrozzino, JA Connor and WF Colmers
Department of Pharmacology, University of Alberta, Edmonton, Canada.
Neuropeptide Y (NPY) is far more abundant in the dentate gyrus than
elsewhere in the hippocampal formation, but it does not alter the synaptic
excitation of dentate granule cells (DGCs) as it does for pyramidal cells
in areas CA1 and CA3. NPY inhibited depolarization- induced increases in
intracellular Ca2+ concentrations ([Ca2+]i) in DGCs in hippocampal slices,
without altering the resting [Ca2+]i. NPY inhibited Ca2+ currents (ICa) via
a Y1 receptor in 84% of acutely isolated DGCs and via a Y2 receptor in 31%
of the NPY-responsive cells tested. ICa inhibition was completely occluded
by omega-conotoxin-GVIA but not by nimodipine. The inhibition of ICa was
accompanied by a change in the time course of ICa activation in only 27% of
NPY- responsive cells. Only 23% of DGCs responded to NPY when Ba2+ was
substituted for extracellular Ca2+ and when [Ca2+]i was strongly buffered.
Therefore, NPY inhibits an N-type ICa in DGCs, mainly via Y1 receptors.
Furthermore, it seems that more than one mechanism, one of which may be
sensitive to [Ca2+]i, may couple NPY receptors to the Ca2+ channels in
DGCs. Because the release of dynorphin from DGCs depends in part on N-type
currents, NPY receptors are poised to regulate the release of opioid
peptides from DGC somata and dendrites.