Behaviour of the transgenic (mREN2)27 rat.

The first model of genetically engineered hypertension, the transgenic rat TGR (mREN2)27, provides a unique opportunity to study the behavioural effects of an altered brain renin-angiotensin system. The TGR (mREN2)27 rats, characterised by fulminant hypertension, show differences in both the peripheral and central angiotensin systems. The behaviour of male transgenic TGR (mREN2)27 and male Sprague-Dawley rats were determined by 4 behavioural tests. While on the elevated X-maze the TGR (mREN2)27 rat showed a greater 'anxiogenic' profile (fewer open arm entries) than the control Sprague-Dawley rats, this 'anxiogenic' profile increased further during a second exposure to the elevated X-maze 24 h later. In comparison the behaviour of the male Sprague-Dawley rats was not different between the two exposures to the elevated X-maze. Locomotor activity did not differ between either the TGR (mREN2)27 or Sprague-Dawley rats when placed in a 1 m2 open-field for 10 min. A short period of fluid-deprivation (3 h) reversed the 'anxiogenic' profile of the TGR (mREN2)27 on the elevated X-maze. Administration of captopril (20 mg . kg-1 body weight) in the drinking water of the TGR (mREN2)27 rats and Sprague-Dawley rats reversed the anxiogenic profile of the TGR (mREN2)27 rat on the elevated X-maze but did not alter the behaviour of the Sprague-Dawley rats.