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Journal Of Tropical Biosciences

Year: 2016|   Volume No: 11|   ISSN: 0795-3089|   Page No: 20


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Title:  VISIO-SPATIAL LEARNING AND MEMORY OUTCOME OF SUB-ACUTE INSULIN ADMINISTRATION IN MICE

I.U.YARUBE1*, J.O. AYO2, R.A. MAGAJI3, I.A. UMAR4, A.W. ALHASSAN3, M.I.A. SALEH3, N.W. YUSUF1

1DEPARTMENT OF PHYSIOLOGY, FACULTY OF BASIC MEDICAL SCIENCES, COLLEGE OF HEALTH SCIENCES, BAYERO UNIVERSITY, KANO-NIGERIA.

2DEPARTMENT OF VETERINARY PHYSIOLOGY, FACULTY OF VETERINARY MEDICINE, AHMADU BELLO UNIVERSITY, ZARIA-NIGERIA.

3DEPARTMENT OF HUMAN PHYSIOLOGY, FACULTY OF MEDICINE, AHMADU BELLO UNIVERSITY, ZARIA-NIGERIA.

 

4DEPARTMENT OF BIOCHEMISTRY, FACULTY OF SCIENCE, AHMADU BELLO UNIVERSITY, ZARIA-NIGERIA.

ABSTRACT

Insulin, mainly used to treat type 1 diabetes mellitus, is now increasingly being used in the treatment of type 2 diabetes mellitus. Apart from its hypoglycaemic effects, insulin was also reported to affect cognition. However, the reported findings on the effect of insulin on visio-spatial learning and memory are scanty and often conflicting. This study aimed to determine the effect of sub-acute insulin administration on learning and memory. Sixteen young mice were divided into two groups and administered daily with insulin (10 I.U./kg) or distilled water (control), subcutaneously for seven days. Learning and memory was assessed using Morris water maze test. The latencies to locate the escape platform in day one was significantly higher than in day two for both insulin-treated (57.92 ± 5.5 s and 55.08 ± 5.9 s) and control (42.50 ± 5.5 s and 30.79 ± 4.9 s) mice, respectively. There was no significant difference in latencies between the two groups. There was also no significant difference in time spent per quadrant and number of platform site crossings within and between groups. It was concluded that sub-acute insulin administration did not impair or improve visio-spatial learning and memory.

SUMMARY:

In this study, the results of the measured parameters - latency to locate the escape platform, time spent in quadrants and number of platform site crossings taken together, indicate that insulin treatment did not impair or improve the ability of the mice to learn, or their long-term memory of the learned task. Insulin has previously been reported to play an important role in normal memory process in Caenorhabditise legans, drosophila, Xenopus, rats and humans (Chiu et al., 2008; Lin et al., 2010; Liu et al., 2013; De Feliceet al., 2014; Chambers et al., 2015; Kim and Feldman, 2015).However, the reported findings on the effects of insulin on visio-spatial learning and memory have been scanty and incongruent. For example, intra-cerebro-ventricular insulin infusion was reported to improve performance in the MWM task of young rats, but no effect in aged ones (Adzovicet al. 2015).Biesselset al. (1998) reported that insulin treatment may prevent, but not reverse deficits in water maze learning and long-term potentiation in streptozotocin-induced diabetic rats. On the contrary, Krikorian (2013) reported that hyperinsulinaemia promotes neurocognitive dysfunction and neurodegenerative changes during the extended, preclinical phase of Alzheimer’s disease. The findings of this study corroborate those of Moosaviet al. (2007) who found no significant effect of low-dose (but not high-dose) intra-hippocampal insulin administration on memory deficit. The findingsare also in agreement with the result of Backeström et al. (2015), who found no association between serum insulin concentration and episodic or semantic memory in middle-aged non-diabetic women.The disparity in the results may be due to multiple factors includingage, sex, specie and strain of the experimental subjects, dose and duration of exposure, as well as differences in apparatus or training procedure and duration.

It was concluded that sub-acute insulin administration did not impair or improvevisio-spatial learning and memory in mice.At this stage of accumulating evidence, it is recommended that further studies be carried out to fully elucidate the effect of insulin on visio-spatial learning and memory.

Correspondence:

E-mail: dryarube@yahoo.com


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