Chronic methylphenidate treatment during adolescence increases anxiety-related behaviors and ethanol drinking in adult spontaneously hypertensive rats

Methylphenidate (MPD) is the most widely used drug in the treatment of attention-deficit hyperactivity disorder (ADHD), the symptoms of which can persist into adolescence and adulthood. The cooccurrence of other psychiatric disorders, such as anxiety and alcoholism, in adults with ADHD is very common, but its etiology remains largely unknown. This study examined the effects of chronic MPD treatment during adolescence on emotional and consummatory behaviors in adult spontaneously hypertensive rats (SHRs), often proposed as an animal model of ADHD. Adolescent SHRs of both sexes were given chronic treatment with MPD (2 mg/kg intraperitoneally; twice daily for 16 days) or vehicle and were subsequently tested in adulthood. The tests used were the open-field and the elevated plus-maze, thought to measure locomotor and emotionality-related behaviors, and a protocol of ethanol consumption. MPD elicited anxious-like behavior in the open-field (but not in the elevated plus-maze) regardless of sex, and enhanced ethanol intake in females. These findings Suggest that MPD treatment during adolescence induces persistent changes on emotionality and ethanol consumption in SHRs, but these effects depend on the sex and behavioral test used. Potential clinical implications of these findings are discussed.