title: Countervailing modulation of Ih by neuropeptide Y and corticotrophin-releasing factor in basolateral amygdala as a possible mechanism for their effects on stress-related behaviors.
abstract: Stress and anxiety-related behaviors controlled by the basolateral amygdala (BLA) are regulated in vivo by neuropeptide Y (NPY) and corticotrophin-releasing factor (CRF): NPY produces anxiolytic effects, whereas CRF produces anxiogenic effects. These opposing actions are likely mediated via regulation of excitatory output from the BLA to afferent targets. In these studies, we examined mechanisms underlying the effects of NPY and CRF in the BLA using whole-cell patch-clamp electrophysiology in rat brain slices. NPY, even with tetrodotoxin present, caused a dose-dependent membrane hyperpolarization in BLA pyramidal neurons. The hyperpolarization resulted in the inhibition of pyramidal cells, despite arising from a reduction in a voltage-dependent membrane conductance. The Y(1) receptor agonist, F(7)P(34) NPY, produced a similar membrane hyperpolarization, whereas the Y(1) antagonist, BIBO3304 [(R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N(2)-(diphenylacetyl)-argininamide trifluoroacetate], blocked the effect of NPY. The NPY-inhibited current was identified as I(h), which is active at and hyperpolarized to rest. Responses to NPY were occluded by either Cs(+) or ZD7288 (4-ethylphenylamino-1,2-dimethyl-6-methylaminopyrimidinium chloride), but unaffected by the G(IRK)-preferring blockers Ba(2+) and SCH23390 [(R)-(+)-7-chloro-8-hydroxy-3-methyl-l-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride]. Application of CRF, with or without TTX present, depolarized NPY-sensitive BLA pyramidal neurons, resulting from an increase in I(h). Electrophysiological and immunocytochemical data were consistent with a major role for the HCN1 subunit. Our results indicate that NPY, via Y(1) receptors, directly inhibits BLA pyramidal neurons by suppressing a postsynaptic I(h), whereas CRF enhances resting I(h), causing an increased excitability of BLA pyramidal neurons. The opposing actions of these two peptides on the excitability of BLA output cells are consistent with the observed behavioral actions of NPY and CRF in the BLA.
authors.affiliation: Department of Pharmacology, School of Molecular and Systems Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Chantelle J
authors.initials: CJ
authors.lastname: Giesbrecht
authors.forename: James P
authors.initials: JP
authors.lastname: Mackay
authors.forename: Heika B
authors.initials: HB
authors.lastname: Silveira
authors.forename: Janice H
authors.initials: JH
authors.lastname: Urban
authors.forename: William F
authors.initials: WF
authors.lastname: Colmers
mesh_terms: D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology / Q000502:physiology*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000378:metabolism; D004347:Drug Interactions; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009478:Neuropeptide Y / Q000494:pharmacology / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D017966:Pyramidal Cells / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017476:Receptors, Neuropeptide Y / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology; D013315:Stress, Psychological / Q000523:psychology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D001552:Benzazepines; D054815:Cyclic Nucleotide-Gated Cation Channels; C578667:Hcn1 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D009478:Neuropeptide Y; D015221:Potassium Channels; D011743:Pyrimidines; D017476:Receptors, Neuropeptide Y; C534628:SCH 23390; C082246:ICI D2788; D002586:Cesium; D001464:Barium; D013779:Tetrodotoxin; D003346:Corticotropin-Releasing Hormone