Study of learning and memory in type 2 diabetic model of zebrafish (Danio rerio)
Shovit Ranjan, Praveen Sharma
Abstract
Type 2 Diabetes (T2D), whose main cause is hyperglycemia, affects the central nervous system, leading to impairment of cognitive functions, which is a major hallmark of certain neurodegenerative disorders in human. These days, zebrafish (Danio rerio) has gained an increasing popularity as a promising model organism for experimental studies of learning and memory. The aim of this study was to investigate the effects of high sucrose induced hyperglycemia or T2D on learning and memory of zebrafish. Hyperglycemia was induced in adult zebrafish by immersion in 83.25 mM sucrose solution for 14 days after performing the study for survival in sucrose solutions. The animals were divided into 2 groups in replicates: control and sucrose-treated hyperglycemic groups. Afterwards, the learning and memory performance was evaluated in both the groups using T-plus maze test and spatial learning test, where zebrafish was required to either associate a visible cue with food reward irrespective of the location of this pairing or associate the spatial location of food reward irrespective of intra-maze cues respectively in two tests. High-sucrose induced hyperglycemic group produced diminished cognitive functions i.e. simple associative and spatial learning abilities by showing less time spent in target arm or zone, lower frequency of target arm or zone visits and total number of arm visits in the experimental apparatus. Overall, our results confirm that an unfamiliar environment of high-sucrose induced hyperglycemia in the zebrafishes are affecting their cognitive abilities. These results further strengthen the view that this complex cognitive ability may be further analyzed using the available genetic tool set for this simple vertebrate.