Brain Disorders: A Pathological Study
Pathologically, addiction is characterized by the pursuit of reward or relief substances in a compulsive, uncontrolled, and debilitating fashion. This behavior occurs as a result of alterations in the mesolimbic pathway of the brain, implicated in reward, motivation, and memory. More specifically, the ventral tegmental area (VTA) and nucleus accumbens are two regions that directly mediate addiction. The VTA, activated by addictive substances, is the site of dopaminergic neurons that project onto the nucleus accumbens in the ventral striatum (Adinoff, 2004). Therefore, studies on addiction usually center around these regions to explore the genetic and neurobiological basis underlying this chronic brain disease. One of the most prominent and
…show more content…
The conditioned place preference (CPP) is a behavioral paradigm in which rodents are repeatedly injected with a drug, in this case cocaine, in a unique chamber. The rodent is then placed in a room connecting the drug-associated chamber to a neutral chamber. Drug addiction is indexed by shorter latency to enter the drug- associated chamber, or lengthened time spent inside of it. In order to ensure that these effects are not specific to the chamber as opposed to the drug itself, the chamber assigned to be the drug-associated one is alternated over many trials (Itzhak & Martin, 2002). However, the major limitation to this paradigm is that it is not a direct measure of addiction, since the drug was administered by the experimenter so whether the rodent wanted it or not is uncertain. In order to circumvent this weakness, paradigms in which the rodent administers the drug itself were developed. These self- administration methods involve either brain or systemic cannulation, where substance infusion occurs every time the rodent pushes on a lever. The advantage to this method is that the injections can be specific and localized, allowing the discernment of brain regions involved in addiction (Panlilio & Goldberg, 2007). Lastly, another popular method used to study addiction and the transition into it is by observing hyperactivity and running patterns using tracking systems. This method is particularly relevant to psychostimulants such as cocaine (Catlow & Kirstein,
The conditioned place preference (CPP) is a behavioral paradigm in which rodents are repeatedly injected with a drug, in this case cocaine, in a unique chamber. The rodent is then placed in a room connecting the drug-associated chamber to a neutral chamber. Drug addiction is indexed by shorter latency to enter the drug- associated chamber, or lengthened time spent inside of it. In order to ensure that these effects are not specific to the chamber as opposed to the drug itself, the chamber assigned to be the drug-associated one is alternated over many trials (Itzhak & Martin, 2002). However, the major limitation to this paradigm is that it is not a direct measure of addiction, since the drug was administered by the experimenter so whether the rodent wanted it or not is uncertain. In order to circumvent this weakness, paradigms in which the rodent administers the drug itself were developed. These self- administration methods involve either brain or systemic cannulation, where substance infusion occurs every time the rodent pushes on a lever. The advantage to this method is that the injections can be specific and localized, allowing the discernment of brain regions involved in addiction (Panlilio & Goldberg, 2007). Lastly, another popular method used to study addiction and the transition into it is by observing hyperactivity and running patterns using tracking systems. This method is particularly relevant to psychostimulants such as cocaine (Catlow & Kirstein,