Caffeine improves spatial learning deficits in an animal model of attention deficit hyperactivity disorder (ADHD) – the spontaneously hypertensive rat (SHR)

• Published in: The international journal of neuropsychopharmacology Vol. 8; no. 4; pp. 583 - 594
• Main Authors: Prediger, Rui D. S., Pamplona, Fabrício A., Fernandes, Daniel, Takahashi, Reinaldo N.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.12.2005; Oxford University Press
• Subjects: Animals; Attention Deficit Disorder with Hyperactivity - psychology; Blood Pressure - drug effects; Caffeine - pharmacology; Central Nervous System Stimulants - pharmacology; Dose-Response Relationship, Drug; Female; Maze Learning - drug effects; Memory - drug effects; Purinergic P1 Receptor Antagonists; Rats; Rats, Inbred SHR; Rats, Wistar; caffeine; spatial learning; spontaneously hypertensive rats (SHR); Attention deficit hyperactivity disorder (ADHD); Morris water maze
• ISSN: 1461-1457; 1469-5111
• DOI: 10.1017/S1461145705005341

The spontaneously hypertensive rat (SHR) is generally considered to be a suitable genetic model for the study of attention deficit hyperactivity disorder (ADHD), since it displays hyperactivity, impulsivity, poorly sustained attention, and deficits in learning and memory processes. Converging evidence suggests a primary role of disturbance in the dopaminergic neurotransmission in ADHD patients and in SHR, and in addition, some studies have also demonstrated alterations in adenosinergic neurotransmission in SHR. In the present study, adult female Wistar (WIS) and SHR rats received caffeine (1–10 mg/kg i.p.) 30 min before training, immediately after training, or 30 min before a test session in the spatial version of the Morris water maze. The effect of caffeine administration on WIS and SHR blood pressure was also measured. SHR needed significantly more trials in the training session to acquire the spatial information, but they displayed a similar profile to that of WIS rats in the test session (48 h later), demonstrating a selective deficit in spatial learning. Pre-training administration of caffeine (1–10 mg/kg i.p.) improved this spatial learning deficit in SHR, but did not alter the WIS performance. In contrast, post-training administration of caffeine (3 mg/kg i.p.) did not alter the SHR test performance, but increased memory retention in WIS rats. No dose of caffeine tested altered the mean blood pressure of WIS or SHR. These results demonstrate a selective spatial learning deficit in SHR which can be attenuated by pre-training administration of caffeine. In addition, the present findings indicate that the spatial learning deficit in SHR is not directly related to hypertension.