The Effect of Methylphenidate on the Microstructure of Schedule-Induced Polydipsia in an animal model of ADHD

• Published in: Behavioural brain research 2017-08, Vol.333, p.211-217
• Main Authors: Íbias, Javier, Daniels, Carter W., Miguéns, Miguel, Pellón, Ricardo, Sanabria, Federico
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Attention Deficit Disorder with Hyperactivity - complications; Attention Deficit Disorder with Hyperactivity - drug therapy; Attention-deficit hyperactivity disorder; Bouts; Central Nervous System Stimulants - therapeutic use; Conditioning, Operant; Disease Models, Animal; Drinking Behavior - drug effects; Drinking Behavior - physiology; Male; Methylphenidate; Methylphenidate - therapeutic use; Polydipsia - drug therapy; Polydipsia - etiology; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Rats, Wistar; Reinforcement Schedule; Schedule-induced polydipsia; Species Specificity; Spontaneously hypertensive rat; Wistar Kyoto rats
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2017.06.048

Schedule-induced polydipsia (SIP) was established in spontaneously hypertensive rats (SHR), Wistar Kyoto rats (WKY), and Wistar rats, using a multiple fixed-time (FT) schedule of food delivery, with 30- and 90-s components. Thereafter, animals were exposed to methylphenidate (MPH; 2.5mg/kg/d) for six consecutive SIP sessions. A test to assess possible sensitization effects was also conducted four days after termination of the drug treatment. At baseline, FT 90-s produced longer and more frequent drinking episodes in SHR than in WKY. An analysis of the distribution of inter-lick intervals revealed that drinking was organized in bouts, which were shorter in SHR than in WKY. Across strains and schedules, MPH shifted drinking episodes towards the beginning of inter-food intervals, which may reflect a stimulant effect on SIP. MPH transiently reduced the frequency of drinking episodes in WKY in FT 30-s, and more permanently reduced the frequency of licking bouts in Wistar rats. MPH also increased the length of licking bouts in Wistar rats. Overall, SHR displayed a hyperactive-like pattern of drinking (frequent but short bouts), which 2.5mg/kg MPH appears to reduce in WKY and Wistar but not in SHR rats. It appears that therapeutic effects of MPH on hyperactive-like SIP require higher doses in SHR relative to control strains.