Noradrenaline and serotonin levels in the guinea pig hippocampus followingunilateral vestibular deafferentation.

Recent evidence indicates that the hippocampus uses input from the vestibul ar system in order to accomplish its spatial computational functions. At pr esent, there are few data on the neurochemical basis of the interactions be tween the vestibular system and the hippocampus. The aim of this study was to determine levels of noradrenaline (NA), serotonin (5-HT) and the 5-HT me tabolite, 5-hydroxyindoleacetic acid (5-HIAA), in the CA1, CA2 and dentate gyrus (DG) regions of the ipsilateral and contralateral hippocampi, at 10 h following deafferentation of the peripheral vestibular nerve (UVD) in guin ea pig, using high-performance liquid chromatography (HPLC) with electroche mical detection (ECD). There were no significant differences in NA levels i n the ipsilateral or contralateral CA1 following UVD. However, there was a significant increase in NA levels in the contralateral CA2 following UVD, c ompared to both the sham and intact anesthetic control conditions (p < 0.05 ). No such change was seen in the ipsilateral CA2. Zn the contralateral DG, there was a significant increase in NA levels in both the UVD and sham con ditions, compared to the intact anesthetic controls (p < 0.05). No signific ant changes in 5-HT or 5-HIAA levels were seen in the ipsilateral or contra lateral CA1, CA2 or DG following UVD. This study provides the first evidenc e that UVD may cause an increase in NA levels in the CA2 region of the cont ralateral hippocampus. (C) 1999 Elsevier Science B.V. All rights reserved.