title: Septal serotonin depletion in rats facilitates working memory in the radial arm maze and increases hippocampal high-frequency theta activity.
abstract: Hippocampal theta activity, which is strongly modulated by the septal medial/Broca׳s diagonal band neurons, has been linked to information processing of the hippocampus. Serotonin from the medial raphe nuclei desynchronises hippocampal theta activity, whereas inactivation or a lesion of this nucleus induces continuous and persistent theta activity in the hippocampus. Hippocampal serotonin depletion produces an increased expression of high-frequency theta activity concurrent with the facilitation of place learning in the Morris maze. The medial septum-diagonal band of Broca complex (MS/DBB) has been proposed as a key structure in the serotonin modulation of theta activity. We addressed whether serotonin depletion of the MS/DBB induces changes in the characteristics of hippocampal theta activity and whether the depletion is associated with learning in a working memory spatial task in the radial arm maze. Sprague Dawley rats were depleted of 5HT with the infusion of 5,7-dihydroxytriptamine (5,7-DHT) in MS/DBB and were subsequently trained in the standard test (win-shift) in the radial arm, while the CA1 EEG activity was simultaneously recorded through telemetry. The MS/DBB serotonin depletion induced a low level of expression of low-frequency (4.5-6.5Hz) and a higher expression of high-frequency (6.5-9.5Hz) theta activity concomitant to a minor number of errors committed by rats on the working memory test. Thus, the depletion of serotonin in the MS/DBB caused a facilitator effect on working memory and a predominance of high-frequency theta activity.
authors.affiliation: Laboratorio de Neuroplasticidad de los Procesos Cognitivos, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico; Laboratorio de Biofísica, Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Mexico.
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: López-Vázquez
authors.affiliation: Laboratorio de Biofísica, Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Mexico.
authors.forename: Elisa
authors.initials: E
authors.lastname: López-Loeza
authors.affiliation: Laboratorio de Neuroendocrinología, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
authors.forename: Naima
authors.initials: N
authors.lastname: Lajud Ávila
authors.affiliation: Laboratorio de Neurofisiología Experimental, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la arboleda 300, Exhacienda de san José de la Huerta, Morelia, Mich C.P. 58341, Mexico.
authors.forename: Blanca Erika
authors.initials: BE
authors.lastname: Gutiérrez-Guzmán
authors.affiliation: Laboratorio de Neurofisiología Experimental, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la arboleda 300, Exhacienda de san José de la Huerta, Morelia, Mich C.P. 58341, Mexico.
authors.forename: J Jesús
authors.initials: JJ
authors.lastname: Hernández-Pérez
authors.affiliation: Laboratorio de Neuroplasticidad de los Procesos Cognitivos, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Mexico.
authors.forename: Yoana Estrada
authors.initials: YE
authors.lastname: Reyes
authors.affiliation: Laboratorio de Neurofisiología Experimental, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Camino de la arboleda 300, Exhacienda de san José de la Huerta, Morelia, Mich C.P. 58341, Mexico.
authors.forename: María Esther
authors.initials: ME
authors.lastname: Olvera-Cortés
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D020667:Diagonal Band of Broca / Q000378:metabolism / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D008570:Memory, Short-Term; D051381:Rats; D017207:Rats, Sprague-Dawley; D020665:Septum of Brain / Q000378:metabolism* / Q000502:physiology; D012701:Serotonin / Q000172:deficiency*; D013826:Theta Rhythm
chemical_list: D012701:Serotonin
keywords: Hippocampus; Septum; Serotonin; Theta activity; Working memory