Abstract
Methylphenidate (MPD) is a widely prescribed psychostimulant used to treat behavioral disorders such as attention deficit hyperactivity disorder (ADHD), as well as for cognitive and memory enhancement across all age groups. In addition, MPD is often used—and abused—recreationally by adolescents, adults, and older individuals. The increasing use of MPD among healthy individuals has raised concerns regarding its potential neurological and behavioral consequences, including dependence and abuse. This study examines the behavioral and neuronal effects of MPD by simultaneously recording neural activity from three key monoaminergic brain regions—the locus coeruleus (LC), dorsal raphe nucleus (DR), and ventral tegmental area (VTA)—in freely behaving adolescent and adult rats. Recording electrodes were implanted in these regions, and both behavior and neural activity were recorded using a wireless telemetry system over ten consecutive days. Rats from each age group were assigned to one of the following five experimental groups: time control, saline control, or one of three MPD treatment groups receiving acute and repeated (chronic) doses of 0.6, 2.5, or 10.0 mg/kg. MPD was administered daily from experimental recording (ER) days 1 to 6 (ER1–6), followed by a three-day washout period (ER7–9), and a rechallenge with saline and MPD on ER10. A total of 2,679 neurons were recorded from 311 adolescent and adult male rats. The results revealed significant age- and brain region-dependent differences in both behavioral and neuronal responses to MPD. These findings emphasize the importance of considering both age and specific brain regions when evaluating the effects of psychostimulants. The data suggests that MPD differentially affects the noradrenergic, serotonergic, and dopaminergic systems in adolescents and adults. Furthermore, repeated MPD exposure produced dependency-like behavioral and neuronal patterns in both age groups, underscoring the need for caution in its therapeutic and non-therapeutic use.
Keywords
Methylphenidate, Ritalin, Neuronal and behavior, Age, Monoamines