Outcome of sub-acute insulin administration on long-term visuo-spatial and short-term working memory in mice

Abstract

Background: In the past, insulin was considered a peripheral hormone, unable to affect the central nervous system. Now, it is well established that insulin occurs in the brain where it exerts regulatory and trophic effects. This study was undertaken to determine the effect of sub-acute insulin administration on long-term visuo-spatial and short-term working memory.

Methods: Twenty four mice, weighing between 18 – 22 g, were used. Two groups of six mice each were used during elevated plus maze and Y-maze, to determine long-term visuo-spatial and short-term spatial working memory, respectively. Control group received deionized water, while insulin group received insulin at 10 I.U./kg/day, subcutaneously.

Results: In the elevated plus maze, acquisition and retention latencies were the same (P > 0.05) when compared between the groups. In the Y-maze test, number of entries into arms was similar (P > 0.05) within and between groups. Time spent in the novel arm by mice in the insulin (103.83 ±7.4 seconds) and control (108.00 ± 13.6 seconds) groups was higher (P < 0.05) when compared to time spent in arm A (68.33 ± 10.0 and 74.50 ± 5.6 seconds, respectively) and B (59.17 ± 9.5 and 69.67 ± 10.7, respectively). Number of triads and percent alternations were also the same (P > 0.05) when compared between the groups.

Conclusion: It was concluded, that sub-acute insulin administration did not affect long-term visuo-spatial memory and short-term working memory in mice.

Keywords: insulin, long-term visuo-spatial memory, short-term spatial memory, working memory, sub-acute treatment