title: Serotonergic modulation of septo-hippocampal and septo-mammillary theta activity during spatial learning, in the rat.
abstract: Theta activity has been related to the processing of spatial information and the formation of hippocampus-dependent memory. The medial septum (MS) plays an important role in the control and coordination of theta activity, as well as in the modulation of learning. It has been established that increased serotonergic activity may desynchronize theta activity, while reduced serotonergic activity produces continuous and persistent theta activity in the hippocampus. We investigate whether serotonin acting on the medial septum could modify spatial learning and the functional relationship between septo-hippocampal and septo-mammillary theta activity. The serotonin was depleted (5HT-D) from the medial septum by the injection of 5,7 DHT (5,7- dihydroxytryptamine). Theta activity was recorded in the dorsal hippocampus, MS and mammillary nuclei (SUM, MM) of Sprague-Dawley male rats during spatial learning in the Morris water maze. Spatial learning was facilitated, and the frequency of the hippocampal theta activity during the first days of training increased (to 8.5Hz) in the 5HT-D group, unlike the vehicle group. Additionally, the coherence between the MS-hippocampus and the MS-mammillary nuclei was higher during the second day of the test compared to the vehicle group. We demonstrated that septal serotonin depletion facilitates the acquisition of spatial information in association with a higher functional coupling of the medial septum with the hippocampus and mammillary nuclei. Serotonin, acting in the medial septum, modulates hippocampal theta activity and spatial learning.
authors.affiliation: Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Michoacán, Mexico; Instituto de Neurobiología, Universidad Nacional Autónoma de México. Querétaro, Querétaro, Mexico. Electronic address: gugube7@yahoo.com.mx.
authors.forename: Blanca Erika
authors.initials: BE
authors.lastname: Gutiérrez-Guzmán
authors.affiliation: Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Michoacán, Mexico; Instituto de Neurobiología, Universidad Nacional Autónoma de México. Querétaro, Querétaro, Mexico.
authors.forename: J Jesús
authors.initials: JJ
authors.lastname: Hernández-Pérez
authors.affiliation: Laboratorio de Neurofisiología Experimental, División de Neurociencias, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, Morelia, Michoacán, Mexico.
authors.forename: María Esther
authors.initials: ME
authors.lastname: Olvera-Cortés
mesh_terms: D000818:Animals; D004102:Dihydroxytryptamines / Q000494:pharmacology; D004569:Electroencephalography; D004924:Escape Reaction / Q000187:drug effects; D006624:Hippocampus / Q000502:physiology*; D007211:Indoles / Q000378:metabolism; D008297:Male; D008326:Mammillary Bodies / Q000187:drug effects / Q000502:physiology*; D018782:Maze Learning / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D020665:Septum of Brain / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D065853:Spatial Learning / Q000187:drug effects / Q000502:physiology*; D018709:Statistics, Nonparametric; D013826:Theta Rhythm / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D004102:Dihydroxytryptamines; D007211:Indoles; C026785:5-hydroxyindole; D012701:Serotonin
keywords: Hippocampus; Mammillary nuclei; Medial septum; Serotonin; Spatial learning; Theta activity