Comparison between intraperitoneal and oral methylphenidate administration: A microdialysis and locomotor activity...

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Methylphenidate (MP) is a common ADHD medication that increases synaptic dopamine (DA).
• Preclinical studies face challenges comparing animal (i.v., i.p.) and human (oral) MP administration routes.
• Understanding route-dependent bioavailability is crucial for interpreting MP's effects.

Purpose of the Study:

• To compare the effects of intraperitoneal (i.p.) and intragastric (oral) methylphenidate (MP) on dopamine (DA) levels and locomotor activity in rats.
• To investigate the impact of administration route on regional brain uptake and plasma levels of MP.
• To clarify how administration route influences MP's neurochemical and behavioral outcomes.

Main Methods:

• In vivo microdialysis to measure nucleus accumbens DA levels in rats.
• Locomotor activity assessment using a photocell apparatus.
• Comparison of brain and plasma levels of radiolabeled [(3)H]MP after i.p. and intragastric administration.

Main Results:

• Intraperitoneal MP (5 and 10 mg/kg) was approximately twice as potent as intragastric MP in increasing extracellular DA and stimulating locomotion.
• A lower dose (2 mg/kg) significantly increased DA and locomotion when administered i.p. but not intragastrically.
• Intraperitoneal administration resulted in higher brain uptake of [(3)H]MP compared to the intragastric route.

Conclusions:

• The route of administration significantly impacts methylphenidate's (MP) neurochemical and behavioral effects.
• Differences in central drug bioavailability between i.p. and intragastric routes explain the observed variations in DA levels and locomotor activity.
• Findings highlight the importance of considering administration route in preclinical MP research for ADHD.