title: Methylphenidate modulates dorsal raphe neuronal activity: Behavioral and neuronal recordings from adolescent rats.
abstract: Methylphenidate (MPD) is a widely prescribed psychostimulants used for the treatment of attention deficit hyperactive disorder (ADHD). Unlike the psychostimulants cocaine and amphetamine, MPD does not exhibit direct actions on the serotonin transporter, however there is evidence suggesting that the therapeutic effects of MPD may be mediated in part by alterations in serotonin transmission. This study aimed to investigate the role of the dorsal raphe (DR) nucleus, one of the major sources of serotonergic innervation in the mammalian brain, in the response to MPD exposure. Freely behaving adolescent rats previously implanted bilaterally with permanent electrodes were used. An open field assay and a wireless neuronal recording system were used to concomitantly record behavioral and DR electrophysiological activity following acute and chronic MPD exposure. Four groups were used: one control (saline) and three experimental groups treated with 0.6, 2.5, and 10.0mg/kg MPD respectively. Animals received daily MPD or saline injections on experimental days 1-6, followed by 3 washout days and MPD rechallenge dose on experimental day (ED)10. The same chronic dose of MPD resulted in either behavioral sensitization or tolerance, and we found that neuronal activity recorded from the DR neuronal units of rats expressing behavioral sensitization to chronic MPD exposure responded significantly differently to MPD rechallenge on ED10 compared to the DR unit activity recorded from animals that expressed behavioral tolerance. This correlation between behavioral response and DR neuronal activity following chronic MPD exposure provides evidence that the DR is involved in the acute effects as well as the chronic effects of MPD in adolescent rats.
authors.affiliation: The University of Texas Health Science Center, Medical School at Houston, Department of Neurobiology and Anatomy, 6431 Fannin St., MSB 7.208B, Houston, TX 77030, USA.
authors.forename: Natasha
authors.initials: N
authors.lastname: Kharas
authors.affiliation: The University of Texas Health Science Center, Medical School at Houston, Department of Neurobiology and Anatomy, 6431 Fannin St., MSB 7.208B, Houston, TX 77030, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Whitt
authors.affiliation: Departmento de Fisiologia Division de Investigacion Universidad Nacional Autonoma de Mexico Mexico City, Mexico.
authors.forename: Cruz
authors.initials: C
authors.lastname: Reyes-Vasquez
authors.affiliation: The University of Texas Health Science Center, Medical School at Houston, Department of Neurobiology and Anatomy, 6431 Fannin St., MSB 7.208B, Houston, TX 77030, USA. Electronic address: nachum.dafny@uth.tmc.edu.
authors.forename: Nachum
authors.initials: N
authors.lastname: Dafny
mesh_terms: D000818:Animals; D059333:Central Nervous System Sensitization / Q000187:drug effects / Q000502:physiology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D065847:Dorsal Raphe Nucleus / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance / Q000502:physiology; D004567:Electrodes, Implanted; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D017207:Rats, Sprague-Dawley; D059015:Wireless Technology
chemical_list: D000697:Central Nervous System Stimulants; D008774:Methylphenidate
keywords: Adolescent; Behavior; Dorsal raphe; Methylphenidate; Neuronal activity; Rats