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The authors—Yong Kim, Merilee A. Teylan, Matthew Baron, Adam Sands, Angus C. Naim (also from Department of Psychology, Yale University School of Medicine, New Haven, Connecticut), and Paul Greengard, all from the Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York City, New York—reported their results in the journal Proceedings of the National Academy of Sciences (PNAS).
Their paper “Methylphenidate-induced dendritic spine formation and ΔFosB expression in nucleus accumbens” (DOI: 10.1073/pnas.0813179106) was published in February 6, 2009 issue of PNAS (and online earlier than that date.)
They state in the paper’s abstract: “Methylphenidate is the psychostimulant medication most commonly prescribed to treat attention deficit hyperactivity disorder (ADHD).”
Methylphenidate (MPH) is a stimulant drug that is prescribed to treat ADHD. It is also used to help treat daytime drowiness (narcolepsy) and chronic fatigue syndrome.
MPH goes by various brand names besides Ritalin, such as Attenta (Australia), Ritalina, Rilatine, Methylin, Penid, and Rubifen.
Ritaline, and other related drugs, have been increasingly used (without a prescription) by people to enhance performance levels in school and to increase the sensation of pleasure.
Based on these prescription and non-prescription uses, the researchers decided to investigate MPH (Ritalin-type drugs) with respect to its risks for addiction.
Page two continues.
They state, “Recent trends in the high usage of methylphenidate for both therapeutic and nontherapeutic purposes prompted us to investigate the long-term effects of exposure to the drug on neuronal adaptation.” [Abstract]
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They then searched for changes in dendritic spine formation, which is associated with the development of synapses and communications among nerve cells.
The researchers were also interested in looking for delta Fos B within the brain, which is involved in the response in the brain to the introduction of illicit drugs that are addictive.
They found that a larger number of “medium-sized” spiny neurons formed in the core and shell of nucleus accumbens (NAcc) from ventral and dorsal striatum. The use of cocaine caused these MSN to form in all types of striatum.
NAcc is a group of neurons in the forebrain that are thought be involved in such sensations as pleasure, laughter, reward, and fear, along with risks from addiction.
Overall, the researchers found that the number of “shorter-sized” spiny neurons increased less for methylphenidate (MPH) than for cocaine, while the number of “longer-sized” spiny neurons increased more for MPH than for cocaine.
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Technically stated: “Chronic methylphenidate increased the density of dendritic spines in MSN-D1 (MSN-expressing dopamine D1 receptors) from the core and shell of nucleus accumbens (NAcc) as well as MSN-D2 (MSN-expressing dopamine D2 receptors) from the shell of NAcc.”
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“In general, the effect of methylphenidate on the increase of shorter spines (class 2) was less than that of cocaine.”
“Interestingly, the methylphenidate-induced increase in the density of relatively longer spines (class 3) in the shell of NAcc was bigger than that induced by cocaine.”
“Furthermore, methylphenidate exposure increased expression of ΔFosB [delta Fos B] only in MSN-D1 from all areas of striatum, and surprisingly, the increase was greater than that induced by cocaine.”
They concluded, “Thus, our results show differential effects of methylphenidate and cocaine on neuronal adaptation in specific types of MSN in reward-related brain regions.”
Thus, methylphenidate (MPH, Ritalin) was found to have similar neurological changes to the brain when compared to cocaine, but those changes were distinct between MPH and cocaine.
However, both chances are associated with the increased risk to drug addiction.
Page four concludes.
Dr. Kim stated, “These changes in neuronal structure and brain chemistry are known to be associated with the process of drug addiction.” [New Scientist (February 7-13, 2009, page 6): “Hooked on Ritalin”]
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However, addiction is more likely when used without a prescription (not under the care of a doctor) by recreational users, such as teenagers looking for pleasure or for performance enhancement at the academic level.
In addition, the study used high doses of MSN so it is thought that prescription use of the drug will not cause addiction, because it is used in lower dosages.
However, since non-prescription use is unregulated by the medical professional, then at higher doses, it would increase the risk of addiction to the recreational user.
For more information on the study, please go to the HON (Health on the Net) News article "Mouse Study Suggests ADHD Drug Might Be Addictive: But expert says finding doesn't apply to patients because doses used were so high."
For more on Ritalin, visit the Drugs.com website "Ritalin."
