Adolescence as a Critical Window for Drug Abuse - Research Study of Neural Correlates of Adolescent Sensitivity and Novel Targets for Pharmacotherapy

Project location: Italy, Milan
Project start date: January 2011 - Project end date: December 2012
Project number: 2010-68
Beneficiary: Università degli Studi di Milano Dipartimento di Scienze Farmacologiche

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The United Nations Office on Drugs and Crime (Unodc) has estimated that people who abused of drugs at least once in 2007 have been between 172 and 250 milions. In Italy, the Minister Giovanardi has illustrated his "Relazione annuale al Parlamento sullo stato delle tossicodipendenze in Italia nel 2008" showing that the most abused drugs have been cocaine, heroin and cannabis. Epidemiological data have clearly shown that, in Italy, there are 385.000 individuals between 15 and 64 years of age who need treatment in the Ser.T. (Servizi Pubblici per le Tossicodipendenze del Sistema Sanitario Nazionale). Further negative data are represented by the time between the first use of the drug of abuse and when people request help in the Ser.T. which might be as long as 14 years, thus underlying the need of an early intervention. Thus, from these data, it clearly appears that abuse of drugs such as cocaine is a huge social problem, primarily when this occurs during adolescence since the consequence of the early abuse is not only the addiction that may result but also the appearance of psychiatric disorders later in life. Thus adolescence, which is indeed a time of vulnerability, might also represent a time of opportunity, if the mechanism of adolescent abuse of cocaine will be better clarified and early treated. For this reason, the research team believes that this research proposal, aimed at understanding the deleterious effects of adolescent abuse of cocaine in the brain, might help in the identification of molecular targets for novel, more specific treatments which could prevent the negative effects of drug abuse.

Adolescence is a period when the brain undergoes many complex changes that can exert long-term influences on decision making and cognitive processes. The fact that initiation of drug taking is so dramatic during the adolescent period is disconcerting suggesting a greater addictive potential during adolescence than at adulthood. Development of the central nervous system during adolescence may play a key role in the increased likelihood to initiate drug use, since adolescence is a critical period of transition from a more emotional regulation of the structures that mediate substance abuse to a more mature cortical regulatory mechanism. Because adolescents lack sufficient cortical regulation (provided by prefrontal cortex), their behavior tends to be more impulsive and guided by emotion than adults, increasing the chances of risky behaviors, thus suggesting that adolescence is a key time period for investigating the development of drug addiction. In addition, young cocaine users have a higher risk for neuropsychiatric disorders, in particular when genetic or environmental predispositions exist, and might be more susceptible to further illicit drug use and dependence. Human studies have, however, some limitations because of the vast heterogeneity of cocaine consumption.
Hence, research with laboratory animals offers an important link to gaining further knowledge about specific effects of cocaine during adolescence and underlying neurobiological mechanisms mediating this heightened susceptibility and releated cognitive- or neuropsychiatric-disorders.
The abuse of psychostimulant and related drugs during adolescence is a neglected issue although its social impact is huge and, therefore, information is lacking on the regulation of important determinants of synaptic plasticity during adolescence: we believe that the investigation of a given target during its maturation (i.e. during adolescence) may provide pivotal information related to its modulation even at later time points, such as adulthood.
The goals of this project which received a grant from the Nando Peretti Foundation are 1) to understand the neurobiological mechanisms that underlie the long-term exposure to cocaine during adolescence and lead to drug dependence that can last into adulthood and 2) to understand the neurobiological mechanisms that underlie the occurrence of psychiatric -related symptoms as a consequence of drug abuse during adolescence.
The research team will focus on two specific targets with a well established role during adolescence: 1) the glutamatergic system and 2) the neurotrophin BDNF (Brain Derived Neurotrophic Factor). They will analyze these targets following cocaine abuse during adolescence at different levels: their transcription and translation; their expression and activation; their subcellular redistribution and sorting and, last but not least, the team will investigate the epigenetic mechanisms set in motion by such adolescential drug treatment in order to have a comprehensive picture of the changes set in motion by abuse of cocaine in this crucial period of life.
Dr. Fabio Fumagalli has all the authorizations for the detention and use of the psychostimulant cocaine for scientific purposes. Animals will be exposed to cocaine treatment (20 mg/kg) during adolescence, from post-natal day 28 to post-natal day 42. At the end of the adolescent treatment with cocaine, half of the animals will be sacrificed on postnatal day 43 (i.e. 24 hours after last drug injection, to investigate the short-term effects of the exposure to cocaine), whereas half of the animals will be left undisturbed in their home cages until adulthood (day 90) when they will be exposed to a repeated stress (2 weeks) and sacrificed thereafter. A maximum of 120 animals will be used throughout the whole experiment. The exposure of the animals to stress is crucial to understand whether cocaine administration during adolescence leads to an altered response to a challenging event like stress: this would be an important information since it is known that psychiatric disorders become manifest at adulthood but may depend on an altered maturation of the brain during adolescence.
The research team believes that this approach may fill a gap of information existing on adolescent cocaine abuse and may provide animal models to develop alternative therapeutic approaches.

Methodology
The research team will use molecular techniques routinely used in its laboratory, i.e. RNase Protection Assay, Real Time PCR, in situ hybridization, immunohistochemistry, western blot, protein-protein immunoprecipitation. These techniques will be applied to the different experimental conditions. Protein expression will be investigated in the whole homogenate but also in the different subcellular compartments, such as the post-synaptic density (PSD), the cytosol and the nucleus to analyze putative changes not only in the expression of the related proteins but also in their distribution.

If young individuals abuse of drugs such as cocaine they are very likely to develop, or to be more prone to develop, addiction as well as psychiatric disorders once adult. To this end, diagnosis of schizophrenia or depression is very often related to abuse of psychostimulants or related drugs during adolescence (as confirmed by epidemiological studies) clearly implying a correlation of adolescent drug abuse with the vulnerability for psychiatric disorders.
Although drug abuse during adolescence places enormous social and economic burden on modern society, it is a neglected disease with respect to funding for basic research. The lack of funding in this field of research is in clear contrast with the relative good amount of funding for other types of disorders such as genetic disorders or neurological disorders, presumably because a social ‘stigma' exist for drug abuse and drug addiction is considered more something to be ashamed of rather than something to fight as a normal disease of the brain. However, these types of basic studies represent an indispensable step to be able, in the future, to find drugs to cure drug abuse.
Concomitantly, the results of the research can be disseminated thoroughly in public schools attended by adolescents: we believe that showing and discussing with them our results can deter these young individuals to start taking these drugs.
The amount of money requested covers the costs of the project plus a fellowship for a young scientist (referred to in Italian as "Borsa per giovani promettenti") who will take his degree in December 2011 and has already manifested his desire to keep doing research in the University lab in order to work on this project during the second year. This will be a great opportunity for this research to complete his formation and, by funding this project, the Nando Peretti Foundation will contribute to the good level of scientific research in Italy in the field of Neuroscience.