Antiepileptic actions of neuropeptide Y in the mouse hippocampus require Y5 receptors.
OBJECTIVE
Recent evidence suggests an antiepileptic role for neuropeptide Y (NPY) in the central nervous system. The precise receptor subtypes mediating the inhibitory actions of NPY in the hippocampal formation, however, remain unclear. In vitro studies suggest a role for Y2 receptors in modulating excitatory hippocampal synaptic transmission and epileptiform discharge. In vivo studies implicate Y5 receptors. Here we used pharmacologic tools and Y5-receptor knockout mice to examine the role of Y5 receptors in mediating the antiexcitatory and antiepileptic actions of NPY in the hippocampal formation.


METHODS
Hippocampal slices were obtained from age-matched wild-type (WT; 129 s3/svimj) and Y5-receptor knockout (Y5R KO) mice generated on the same background strain. Extracellular or whole-cell voltage-clamp recordings were obtained in area CA3 pyramidale. Evoked population spikes or excitatory postsynaptic currents were monitored during bath application of NPY, NPY13-36, or human pancreatic polypeptide (hPP). In some slices, zero-magnesium cerebrospinal fluid (CSF) was used to evoke spontaneous epileptiform discharges.


RESULTS
NPY and NPY agonists with preference for either Y2 (NPY13-36) or Y5 (hPP) receptor subtypes caused a significant reduction in population spike and excitatory postsynaptic current (EPSC) amplitudes in slices from WT mice. NPY (and NPY agonists) also suppressed zero-magnesium epileptiform burst discharge in slices from WT mice. In contrast, bath application of NPY, NPY13-36, or hPP had no effect in slices from Y5R KO mice.


CONCLUSIONS
NPY modulates excitatory synaptic transmission and inhibits limbic seizure activity in the mouse hippocampus. The antiepileptic actions of NPY, in the mouse, appear to require activation of hippocampal Y5 receptors.
Baraban
Scott C
SC
Department of Neurological Surgery, University of California-San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA. baraban@itsa.ucsf.edu
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D051379:Mice; D009478:Neuropeptide Y / Q000494:pharmacology*; D010191:Pancreatic Polypeptide / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D017476:Receptors, Neuropeptide Y / Q000502:physiology*; D012016:Reference Values
D000927:Anticonvulsants; D009478:Neuropeptide Y; D010446:Peptide Fragments; D017476:Receptors, Neuropeptide Y; C100568:neuropeptide Y5 receptor; C059889:neuropeptide Y (18-36); D010191:Pancreatic Polypeptide