title: Orexinergic theta rhythm in the rat hippocampal formation: In vitro and in vivo findings.
abstract: Previous in vivo data suggested that orexin neuropeptides (ORX(A) and ORX(B) ) synthetized in hypothalamic neurons were involved in the mechanism of generation of the hippocampal formation theta rhythm. Surprisingly, this suggestion has never been directly proved by experiments using intraseptal or intrahippocampal administration of orexins. In this study, involving the use of in vitro hippocampal formation slices and in vivo model of anesthetized rat, we provide the first convergent electropharmacological evidence that in the presence of both ORX(A) and ORX(B) the hippocampal formation neuronal network is capable of producing oscillations in the theta band. This effect of orexin peptides was antagonized by selective blockers of orexin receptors (OX1 R and OX2 R), SB 334867 and TCS OX2 29, respectively. These results provide evidence for a novel, orexinergic mechanism responsible for the production of theta rhythm in the hippocampal formation neuronal network.
authors.affiliation: Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Poland.
authors.forename: Renata
authors.initials: R
authors.lastname: Bocian
authors.affiliation: Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Poland.
authors.forename: Paulina
authors.initials: P
authors.lastname: Kazmierska
authors.affiliation: Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Poland.
authors.forename: Paulina
authors.initials: P
authors.lastname: Kłos-Wojtczak
authors.affiliation: Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kowalczyk
authors.affiliation: Department of Neurobiology, Faculty of Biology and Environmental Protection, University of Lodz, Poland.
authors.forename: Jan
authors.initials: J
authors.lastname: Konopacki
mesh_terms: D000818:Animals; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009415:Nerve Net / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000068796:Orexin Receptor Antagonists / Q000494:pharmacology*; D000068797:Orexins / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013826:Theta Rhythm / Q000187:drug effects / Q000502:physiology*
chemical_list: D000068796:Orexin Receptor Antagonists; D000068797:Orexins
keywords: hippocampal formation; in vitro; in vivo; orexin peptides; theta oscillations