ABSTRACT
Twenty 5-week-old male Wistar rats were divided into two groups: one group was fed a fish oil-deficient diet and the other group was fed the same diet supplemented with per orally administered docosahexaenoic acid (DHA) for 12 weeks. Six weeks after the start of the administration of DHA, rats were trained for 6 weeks to acquire a reward at the end of each of four arms of an eight-arm radial maze. On completion of the radial maze task, the Fos expression in the hippocampus was examined immunohistochemically. Chronic DHA administration significantly reduced the number of reference and working memory errors. The number of Fos-positive neurons in the CA1 hippocampus significantly increased in DHA-treated rats compared with control rats, demonstrating a statistically significant negative correlation with the number of reference memory errors. These results suggest that the DHA-induced improvement in spatial cognition is associated with increased Fos expression in the CA1 hippocampus.
Subject(s)
Diet , Docosahexaenoic Acids/pharmacology , Genes, fos/drug effects , Hippocampus/metabolism , Memory/drug effects , Space Perception/drug effects , Animals , Gene Expression/drug effects , Hippocampus/drug effects , Male , Maze Learning/drug effects , Memory, Short-Term/drug effects , Neurons/drug effects , Neurons/metabolism , Rats , Rats, WistarABSTRACT
The preoptic area (POA) occupies a crucial position among the structures participating in thermoregulation, but we know little about its efferent projections for controlling various effector responses. In this study, we used an immunohistochemical analysis of Fos expression during local warming of the preoptic area. To avoid the effects of anesthesia or stress, which are known to elicit Fos induction in various brain regions, we used a novel thermode specifically designed for chronic warming of discrete brain structures in freely moving rats. At an ambient temperature of 22 degrees C, local POA warming increased Fos immunoreactivity in the supraoptic nucleus (SON) and the periaqueductal gray matter (PAG). Exposure of animals to an ambient temperature of 5 degrees C induced Fos immunoreactivity in the magnocellular paraventricular nucleus (mPVN) and the dorsomedial region of the hypothalamus (DMH). Concurrent warming of the POA suppressed Fos expression in these areas. These findings suggest that thermal information from the preoptic area sends excitatory signals to the SON and the PAG, and inhibitory signals to the mPVN and the DMH.