Hippocampal 5-HT and NE release in the transgenic rat TGR(mREN2)27 related to behavior on the elevated plus maze

The transgenic rat TGR(mREN2)27 was generated to study mechanisms involved in the hypertensive process. A characteristic of this rat is a high expression of the murine renin-2 gene in several peripheral tissues and in the brain. The high expression of the transgene is associated with increased local formation of angiotensin II. In a previous study, we studied for the first time the behavior of male TGR(mREN2)27 rat in the open field and on the elevated plus maze. There were no differences between TGR(mREN2)27 and SPRD-controls in locomotor activity measured in the open field. While placed on the elevated plus maze, however, the TGR(mREN2)27 rats showed a greater "anxiogenic" profile than the SPRD-rats. The present study was aimed to characterize neurotransmitter release involved in anxiety in hippocampus of TGR(mREN2)27 rats during exposure to the elevated plus maze. Exposure to the maze resulted in an increased intrahippocampal serotonin release with the same maximum both in the transgenic rats and in the control rats. However, the subsequent decrease was significantly faster in the TGR(mREN2)27 compared to the SPRD-controls. The latter suggests that the serotonergic system is functionally changed in the TGR(mREN2) rat, too. In contrast, norepinephrine release did not change during exposure to the maze and there were no significant differences in norepinephrine release between transgenics and controls.