Spontaneously hypertensive and Wistar Kyoto rats differ in delayed matching-to-place performance and response to dietary long-chain polyunsaturated fatty acids

Abstract

Spontaneously hypertensive rats (SHR) were used as an animal model of attention deficit hyperactivity disorder (ADHD). This study investigated whether, in comparison with its progenitor strain, Wistar-Kyoto rats (WKY), SHR would show deficits in spatial short-term memory in the delayed-matching-to-place (DMP) version of the Morris water maze and be more distracted by exposure to a novel stimulus during recall trials. It also addressed whether dietary supplementation with long-chain polyunsaturated fatty acids (LCPUFA) during development would increase brain docosahexaenoic acid (DHA) and improve SHR behavioral performance. Beginning at weaning (21 days), male SHR and WKY were fed either a control or LCPUFA supplemented diet [0.5% arachidonic acid (AA) and 0.9% DHA], and behavioral testing began at 8 weeks. The first three tasks comprised a series of problems, each consisting of an initial search trial and subsequent recall trials. The intertrial interval (ITI) between the search and recall trial was either 60 s or 60 min. Surprisingly, in contrast to SHR, WKY did not appear to use a spatial short-term memory strategy to solve the problem. Notwithstanding, the performance of both strains was affected by the delay, such that they showed longer path lengths at the long compared with the short ITI. There was no effect of dietary supplementation on DMP performance. SHR fed the control diet were less responsive to a novel stimulus introduced on the first recall trial than WKY, and this tended to increase with supplementation. Analysis of brain fatty acid composition indicated that supplementation did increase DHA in the phosphatidylethanolamine fraction in WKY; however, in SHR, there was either no change (phosphatidylethanolamine) or paradoxical decreases (phosphatidylcholine and phosphatidyserine/phosphatidylinositol). Further research is needed to determine whether SHR are an appropriate model for studying a possible relationship between dietary LCPUFA and the behavioral symptoms of ADHD.