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Effects of subchronic methylphenidate hydrochloride administration on the locomotor and exploratory behavior of
N Carrey1, M P McFadyen, R E Brown
1Department of Outpatient Psychiatry, IWK-Grace Hospital, Halifax, Nova Scotia, Canada. ncarrey@iwkgrace.ns.ca
Abstract:
The increasing use of methylphenidate hydrochloride (MPH) in children led us to examine the effects of MPH administration in developing mice. Male CD-1 mice were administered MPH (40 mg/kg, subcutaneously) or saline daily from postnatal days 26-32. The mice were then tested from postnatal days 33-37 for locomotion and exploration in the open field, anxiety in the elevated plus maze, and learning in the Morris water maze. The results indicate that MPH-pretreated mice were more exploratory and less fearful in the open field, entering more center squares than saline controls. MPH-pretreated mice also exhibited less anxiety, spending more time in the open arm and exhibiting more head dips in the elevated plus maze than controls. There was no significant difference between MPH and saline-treated mice in the time taken to find the visible or hidden platform in the water maze task. The results indicate that treatment with MPH has significant effects on later behavior, reducing fear and anxiety, and increasing exploration, but no effect on performance in a spatial learning task.
Insights
Methylphenidate hydrochloride (MPH) given to young mice reduced fear and anxiety behaviors, while increasing exploration. However, MPH did not impact spatial learning abilities in the Morris water maze task.
Area of Science:
- Neuroscience
- Developmental Psychology
- Pharmacology
Background:
- Methylphenidate hydrochloride (MPH) is increasingly prescribed for children.
- Understanding MPH's effects on the developing brain is crucial.
Purpose of the Study:
- To investigate the behavioral effects of MPH administration during a critical developmental period in mice.
- To assess MPH's impact on locomotion, anxiety, and spatial learning.
Main Methods:
- Male CD-1 mice received daily subcutaneous injections of MPH (40 mg/kg) or saline from postnatal days 26-32.
- Behavioral testing occurred from postnatal days 33-37, including open field, elevated plus maze, and Morris water maze.
- Locomotion, exploration, anxiety levels, and spatial learning were measured.
Main Results:
- MPH-treated mice showed increased exploration and reduced fear in the open field.
- MPH administration led to decreased anxiety behaviors in the elevated plus maze.
- No significant differences in spatial learning were observed between MPH and saline groups in the water maze.
Conclusions:
- Early-life MPH exposure significantly alters later behavior, reducing fear and anxiety while enhancing exploration.
- MPH treatment does not appear to affect spatial learning capabilities in this developmental model.
- These findings highlight the nuanced impact of MPH on neurobehavioral development.