Effect of melatonin on exploration and anxiety in normotensive and hypertensive rats with high activity of renin-angiotensin system.
OBJECTIVES: The purpose of the study was to investigate effects of melatonin (MEL) on exploration and anxiety in normotensive Sprague-Dawley (SD) and hypertensive TGR(mREN2)27 (TGR) rats with high activity of renin-angiotensin system.
METHODS: Mature control (n=20) and hypertensive (n=20) rats were used. Half of each group was treated with MEL in drinking water (40 microg/ml) for 3 weeks. The influence of MEL on exploration was measured in the open field test (OF) and on anxiety in the elevated plus maze test (EPM).
RESULTS: Hypertensive TGR rats showed a lower level of ambulation (p<0.05) and higher level of urination (p<0.001) in OF. In EPM they spent more time in closed arms (p<0.05) and showed low frequency of total arm entries (p<0.01) than SD rats. MEL treated SD rats exhibited increased ambulation (p<0.01), sniffing (p<0.05) and decreased creeping (p<0.05) in OF than SD controls and did not exhibit differences in behaviour observed in EPM. MEL treated TGR rats exhibited a decrease in creeping, defecation and urination (p<0.05) in OF and spent less time in closed arms (p<0.05) and increased frequency of total arm entries (p<0.05) in EPM than untreated TGR animals.
CONCLUSION: Our results suggest that MEL decreased anxiety related behaviours in hypertensive rats with an up regulated renin-angiotensin system and stimulated active exploration of control animals....
Citation
Krsková L, Vrabcová M, Zeman M. Effect of melatonin on exploration and anxiety in normotensive and hypertensive rats with high activity of renin-angiotensin system. Neuro Endocrinol Lett. 2007 Jun; 28(3): 295-301