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Disruption of sensitization to methylphenidate by a single administration of MK-801
Osvaldo Gaytan1, Alan C Swann, Nachum Dafny
1Department of Neurobiology and Anatomy, The University of Texas Health Science Center at Houston, 77030, USA.
Abstract:
Blockade of sensitization to methylphenidate by a single injection of MK-801 was investigated using a computerized activity monitoring system. Male Sprague-Dawley rats were housed in test cages and motor activity was recorded continuously for 16 days. After 2 days of baseline recording and a saline injection on day 3, the rats were randomly divided into four experimental groups. All received 2.5 mg/kg of methylphenidate (s.c.) once a day from days 4 to 9, then after five days of no treatment, they were re-challenged with 2.5 mg/kg of methylphenidate on day 15. One group received only methylphenidate, while the other three groups also received a single i.p. injection of MK-801 (0.30 mg/kg) either 24 h (day 3) or 1 h prior to the first of the six methylphenidate injections (day 4), or 1 h prior to the second methylphenidate injection (day 5). A single injection of MK-801 on day 4 (1 h prior to methylphenidate) blocked the development of sensitization to methylphenidate, since a sensitized response could not be elicited six days after cessation of repeated methylphenidate administration (day 15). However, sensitization to methylphenidate still occurred in the groups receiving MK-801 (0.30 mg/kg) on day 5, indicating that the mechanism by which a single injection of MK-801 disrupts sensitization to methylphenidate is sensitive to timing and is not a direct long-term effect. In conclusion, a single injection of MK-801 persistently blocks the development of sensitization to methylphenidate only if it is given with methylphenidate on the first day of the repetitive treatment phase.
Insights
A single injection of MK-801 blocked methylphenidate sensitization in rats when administered concurrently with the first dose. This effect was time-dependent, indicating MK-801
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Methylphenidate is a widely used stimulant medication.
- Repeated administration of methylphenidate can lead to behavioral sensitization.
- The NMDA receptor antagonist MK-801 has been implicated in modulating drug-induced neuroplasticity.
Purpose of the Study:
- To investigate the effect of a single MK-801 injection on the development of methylphenidate sensitization.
- To determine the critical timing for MK-801's blockade of methylphenidate sensitization.
Main Methods:
- Male Sprague-Dawley rats were used in a computerized activity monitoring system.
- Rats received daily methylphenidate injections for six days, with or without a single MK-801 injection at different time points.
- Motor activity was recorded to assess sensitization development and blockade.
Main Results:
- A single injection of MK-801 administered 1 hour prior to the first methylphenidate dose on day 4 blocked the development of sensitization.
- Sensitization to methylphenidate still occurred when MK-801 was administered on day 5, one hour before the second methylphenidate dose.
- The blockade of sensitization by MK-801 was dependent on the timing of administration relative to methylphenidate treatment.
Conclusions:
- A single injection of MK-801 can persistently block the development of methylphenidate sensitization.
- The timing of MK-801 administration is crucial for its sensitizing-blocking effect.
- This suggests a time-sensitive mechanism underlying MK-801's disruption of methylphenidate-induced neuroplasticity.