Hippocampal serotonin depletion facilitates place learning concurrent with an increase in CA1 high frequency theta activity expression in the rat.
Acetylcholine- and serotonin-dependent theta activities have been long proposed to exist. However, several studies have shown that serotonin tends to desynchronise hippocampal EEG activity. Theta activity has been related to the processing of hippocampal place learning. Since the serotonergic system can influence hippocampal theta activity, it could function as a modulator of spatial learning. For these reasons, we investigated the possible role of hippocampal serotonin in the regulation of theta activity during the acquisition of map-based spatial information. Following 5-HT hippocampal depletion through 5,7-dihydroxytriptamine-induced lesions to the fimbria, fornix and cingulate bundle of adult rats, CA1 hippocampal theta activity was recorded during place learning training. Only rats with reduction higher than 90% from controls, verified post-mortem by HPLC were studied. A facilitation of place learning after hippocampal serotonin depletion occurred, and was associated with earlier expression of dominant high frequency theta activity (6.5-9.5Hz). Therefore, theta activity was related to the accuracy of behavioural performance through 5-HT modulation in a place learning test.
Laboratorio de Neurofisiología Experimental, Centro de Investigación Biomédica de Michoacán; Instituto Mexicano del Seguro Social, México. gugube7@yahoo.com.mx
Blanca Erika
BE
Gutiérrez-Guzmán
J Jesús
JJ
Hernández-Pérez
Ignacio
I
González-Burgos
Alfredo
A
Feria-Velásco
Rafael
R
Medina
Miguel Ángel
MÁ
Guevara
Miguel Ángel
MÁ
López-Vázquez
María Esther
ME
Olvera-Cortés
D015116:5,7-Dihydroxytryptamine; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D007858:Learning / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000172:deficiency / Q000378:metabolism*; D013028:Space Perception / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*
D015116:5,7-Dihydroxytryptamine; D012701:Serotonin