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Neuro Endocrinol Lett. 2007 Jun;28(3):295-301.

Effect of melatonin on exploration and anxiety in normotensive and hypertensive rats with high activity of renin-angiotensin system.

Author information

1
Comenius University, Faculty of Natural Science, Department of Animal Physiology and Ethology, Bratislava, Slovakia. krskova@fns.uniba.sk

Abstract

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.

PMID:
17627265
[Indexed for MEDLINE]
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