Galanin n-terminal fragment (1-15) induces an anxiety- and depressive-like behaviours in the light/dark and tail suspension tests

Galanin N-terminal fragment (1-15) [Gal(1-15)] is involved in mood regulation. We have shown that intracerebroventricular (icv) administration of Gal(1-15) produces a depressive-like behaviour in the forced swim test (FST) and an anxiety-like behaviour in the open field test (OF) in rats. In this work we analyze the effect of Gal(1-15) in two more behavioural tests, the tail suspension test (TLT) and the light/dark test. In light/dark test we studied during 5 min the latency time for entering the dark box, time spent in the light compartiment, and the latency time for re-entering the light box as parameters indicators of anxiety-like behaviour. In TLT total immobility time was analyzed during 6 min test as parameter indicator of depressive-like behaviour. Groups of rats (n=5-8) were injected icv with Gal(1-15) 3nmol, a dose effective in FST and OF, or artificial cerebrospinal fluid 15 minutes before the test. Behavioural assessment were conducted with at least one week between tests. Student’s t-test was used for comparation between experimental groups. In the light/dark test Gal(1-15) 3nmol significantly reduced the time spent in the light compartiment by 52% (p<0.05) and the latency time for entering the dark box by 65% (p<0.05). An increased in the latency time for re-entering the light box was also observed (p<0.05). This pattern of results reflects an anxiogenic-like effects of Gal(1-15) in this test. In the TST, the administration of Gal(1-15) 3nmol significantly increased rat immobility by 16% (p