Document Type

Restricted

Advisor

Joseph Schroeder

Publication Date

2025

Comments

Access to this paper is restricted to the Connecticut College campus until June 5, 2027.

Abstract

Attention-Deficit/Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder that affects more than 6.5 million children and 15.5 million adults in the US (Danielson, et al., 2024; Staley, et al., 2023). One medication for ADHD is methylphenidate (MPH), a psychostimulant that increases dopamine (DA). Caffeine (CAF) is a more accessible psychostimulant that has unclear effects on ADHD (Perrotte, et al., 2023). To study the effects of CAF and MPH on ADHD, this study utilized a rat model of ADHD called the Spontaneously Hypertensive Rat (SHR). Rats underwent Barnes Maze testing for Working Memory (WM), Long-Term Memory (LTM), and hyperactivity. It was hypothesized that animals exposed to MPH would perform better on all measures of memory and demonstrate reduced hyperactivity than the CAF group, which in turn would perform better than the saline-exposed group (SAL). For WM, during reversal learning, female (F) rats performed consistently better on WM, and the male (M) CAF and M MPH groups performed better than the M SAL group. For LTM, animals treated with CAF performed the worst during learning, but a pattern following the hypothesis (MPH better than CAF, which was better than SAL) was shown in reversal learning. In the probes, the only differences were by sex, where the males performed better than the females, and the M SAL group performed better than both the M CAF and M MPH groups in reversal learning. For hyperactivity, F SAL and F CAF groups were more hyperactive than M SAL and M CAF, but M MPH was more hyperactive than the F MPH group. Overall, this indicates that sex differences are critical when using SHRs as models of ADHD. In addition, MPH increased hyperactivity instead of reducing it like in humans. Future studies should use caution when applying research using SHRs to both females and males if they do not examine sex differences.

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The views expressed in this paper are solely those of the author.