Methylphenidate differentially affects the social ultrasonic vocalizations of wild-type and prodromal Parkinsonian rats.

Prodromal signs of Parkinson's disease (PD), including vocal communication deficits, are poorly understood and do not respond adequately to current pharmacologic treatments. Norepinephrine dysfunction is involved early in PD; thus, drug therapies targeting norepinephrine may be useful as a treatment of prodromal signs. This study used a validated, translational rodent model of prodromal PD, the male -/- rat, which exhibits ultrasonic vocalization (USV) deficits as early as 2 months of age. The purpose of this preclinical study was to investigate a dose-dependent (2.5, 5.0, 7.5, 10 mg/kg) response of methylphenidate on USV parameters with the hypothesis that methylphenidate would increase vocalization output. Because methylphenidate is a psychostimulant with known adverse side effects, we also hypothesized that potential side effects including anxietylike behavior and spontaneous activity would be increased in a dose-dependent manner. To accomplish this, wild-type (WT) and -/- rats were administered a dose of a vehicle (saline) and a methylphenidate dose in a randomized within-subjects design and then assessed for USVs, anxiety behavior (open field), and limb motor (cylinder) activity. The results suggest that methylphenidate does not alter USV emissions in -/- rats; however, methylphenidate increased the total number of vocalizations and duration of frequency-modulated calls in WT rats. Methylphenidate dose dependently influenced spontaneous movements in both WT and -/- rats, as expected, while methylphenidate increased anxiety in -/- rats and not WT rats. This study demonstrates a difference in response to a psychostimulant between -/- rats and WT rats. (PsycInfo Database Record (c) 2025 APA, all rights reserved).