The Journal of Neuroscience, August 1, 2001, 21(15):5804-5812
Plasticity of Y1 and Y2 Receptors and Neuropeptide Y Fibers in
Patients with Temporal Lobe Epilepsy
Sabine
Furtinger1,
Susanne
Pirker1,
Thomas
Czech3,
Christoph
Baumgartner4,
Gerhard
Ransmayr2, and
Günther
Sperk1
Departments of 1 Pharmacology and
2 Neurology, University of Innsbruck, A-6020 Innsbruck,
Austria, and Departments of 3 Neurosurgery and
4 Neurology, University of Vienna, A-1090 Vienna, Austria
Marked expression of neuropeptide Y (NPY) and its Y2 receptors in
hippocampal mossy fibers has been reported in animal models of
epilepsy. Because NPY can suppress glutamate release by activating presynaptic Y2 receptors, these changes have been proposed as an
endogenous protective mechanism. Therefore, we investigated whether
similar changes in the NPY system may also take place in human
epilepsy. We investigated Y1 and Y2 receptor binding and NPY
immunoreactivity in hippocampal specimens that were obtained at surgery
from patients with temporal lobe epilepsy and in autopsy controls.
Significant increases in Y2 receptor binding (by 43-48%) were
observed in the dentate hilus, sectors CA1 to CA3, and subiculum of
specimens with, but not in those without, hippocampal sclerosis. On the
other hand, Y1 receptor binding was significantly reduced (by 62%) in
the dentate molecular layer of sclerotic specimens. In the same
patients, the total lengths of NPY immunoreactive (NPY-IR)
fibers was markedly increased (by 115-958%) in the dentate molecular layer and hilus, in the stratum lucidum of CA3, and throughout sectors CA1 to CA3 and the subiculum, as compared with autopsies. In nonsclerotic specimens, increases in lengths of NPY-IR
fibers were more moderate and statistically not significant. NPY mRNA
was increased threefold in hilar interneurons of sclerotic and
nonsclerotic specimens. It is suggested that abundant sprouting of NPY
fibers, concomitant upregulation of Y2 receptors, and downregulation of
Y1 receptors in the hippocampus of patients with Ammon's horn sclerosis may be endogenous anticonvulsant mechanisms.
Key words:
NPY; hippocampus; limbic system; dentate gyrus; presynaptic receptors; Ammon's horn sclerosis; neuropeptides; seizures
Copyright © 2001 Society for Neuroscience 0270-6474/01/21155804-09$05.00/0