title: MK-801 blocks the development of sensitization to the locomotor effects of methylphenidate.
abstract: Male Sprague-Dawley rats were divided to three groups (each n = 8) and were housed in test cages where motor activity was recorded continuously for 16 days using a computerized motor activity monitoring system to determine whether repeated administration of MK-801 could block the development and/or the expression of sensitization to the locomotor effects of methylphenidate (MPD). One group of rats received six daily injections (days 4-9) of 0.30 mg/kg MK-801, followed by 5 days without injection (days 10-14) and re-challenged (day 15) with 0.30 mg/kg MK-801. The second group received a challenge dose of 2.5 mg/kg MPD (day 4) followed by 5 days of co-treatment with MK-801 (0.30 mg/kg) given 1 h prior to MPD (days 5-9). This group was then re-challenged with MPD (2.5 mg/kg) on day 15. The last group received six daily injections of 2.5 mg/kg MPD (days 4-9). They were then split into two subgroups of rats which received either no treatment (control) or five daily injections of 0.30 mg/kg MK-801 (days 10-14) before being re-challenged on day 15 with 2.5 mg/kg MPD. MK-801 sensitized to its own locomotor effects. MK-801 given after sensitization had developed (i.e., days 10-14) was able to mask the expression of a sensitized response on day 15, but the effect was only transient since the sensitized response was present 3 weeks later. Moreover, MK-801, when coadministered during the repeated treatment phase was able to block the development of a sensitized response, which suggest that NMDA receptors involved in the process of MPD sensitization.
authors.affiliation: Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, TX 77225, USA.
authors.forename: O
authors.initials: O
authors.lastname: Gaytan
authors.forename: R
authors.initials: R
authors.lastname: Nason
authors.forename: R
authors.initials: R
authors.lastname: Alagugurusamy
authors.forename: A
authors.initials: A
authors.lastname: Swann
authors.forename: N
authors.initials: N
authors.lastname: Dafny
mesh_terms: D000818:Animals; D016739:Behavior, Addictive / Q000188:drug therapy* / Q000503:physiopathology*; D001921:Brain / Q000187:drug effects / Q000503:physiopathology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D000697:Central Nervous System Stimulants; D004338:Drug Combinations; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D008774:Methylphenidate; D016291:Dizocilpine Maleate