Aims: 

This study investigated the relationship between open field behaviour, blood pressure (BP), body weight and nitric oxide (NO) production in the hypothalamus and cerebellum of rats with normal and elevated BP.

Methods: 

Open field (100x100 cm, 10 min) behaviour was determined in adult normotensive Wistar-Kyoto (WKY) rats, borderline hypertensive rats (BHR) and spontaneously hypertensive rats (SHR). BP was measured by tail cuff method. NO synthase activity was determined by conversion of [3H]-L-arginine.

Results: 

BP of WKY, BHR and SHR was 104±2, 141±5 and 192±3 mmHg, respectively (p< 0.01 among all). Body weight of WKY, BHR and SHR was 427±8, 476±9 and 388±7 g, respectively (p< 0.01 among all). Total distance travelled of WKY was 15±0.8m and it was elevated significantly in both BHR (22±3m) and SHR (25±1m). Time spent and distance travelled in the central zone (55x55 cm) were also increased significantly in BHR and SHR vs. WKY. Immobility time in the central and peripheral zones was reduced significantly in hypertensive rats. In contrast, distance travelled in the peripheral zone did not differ significantly among the groups. Horizontal motor activity of rats in the open field correlated with BP (total distance travelled: r=0.66 p< 0.001; total immobility time: r=-0.897, p< 0.001) but not with body weight. NOS activity in the hypothalamus and cerebellum of WKY, BHR and SHR did not differ significantly and no association between NO production and open field activity was observed.

Conclusion: 

Results showed that hypertensive rats were hyperactive in the open field and the level of their hyperactivity was associated rather with BP than with body weight or disturbances in NO production in the hypothalamus or cerebellum.

Study was supported by the grants APVV-0523-10 and VEGA 2/0084/10.