A few of my close family members have struggled with addiction. So, I constantly think about the behavioral changes that occur in response to substance dependency. I am excited that I have reached a point where I can learn about the behavior and neural mechanisms that are involved in various addictions.
Now onto the subject of this post… A woman once told me a story about a man who decided to get clean after decades of drug and alcohol abuse. He turned his life around by joining AA/NA programs and moving out of the space that triggered his desire to do drugs. After being “clean” for 20 years, he relapsed. My next question was why? 20 years is such a long time. This woman explained that feeling too overwhelmed or stressed can trigger relapse. So what does that look like on a molecular level? I am unsure, but I found a really sweet article on neurogenesis and relapse. The most important finding was that reducing neurogenesis before self-administration of cocaine increased the chances of relapse (Noonan, 2010; please see abstract below). Perhaps we are seeing the neuroprotection idea. Basically, new neurons may protect the hippocampus from future insults. Decreasing the number of neurons may exacerbate the novelty of these drugs and predispose them to addiction. Is this logical possible?
Title: Reduction of adult hippocampal neurogenesis confers vulnerability in an animal model of cocaine addiction.
Drugs of abuse dynamically regulate adult neurogenesis, which appears important for some types of learning and memory. Interestingly, a major site of adult neurogenesis, the hippocampus, is important in the formation of drug– context associations and in the mediation of drug-taking and drug-seeking behaviors in animal models of addiction. Correlative evidence suggests an inverse relationship between hippocampal neurogenesis and drug-taking or drug-seeking behaviors, but the lack of a causative link has made the relationship between adult-generated neurons and addiction unclear. We used rat intravenous cocaine self-administration in rodents, a clinically relevant animal model of addiction, to test the hypothesis that suppression of adult hippocampal neurogenesis enhances vulnerability to addiction and relapse. Suppression of adult hippocampal neurogenesis via cranial irradiation before drug-taking significantly increased cocaine self-administration on both fixed-ratio and progressive-ratio schedules, as well as induced a vertical shift in the dose–response curve. This was not a general enhancement of learning, motivation, or locomotion, because sucrose self-administration and locomotor activity were unchanged in irradiated rats. Suppression of adult hippocampal neurogenesis after drug-taking significantly enhanced resistance to extinction of drug-seeking behavior. These studies identify reduced adult hippocampal neurogenesis as a novel risk factor for addiction-related behaviors in an animal model of cocaine addiction. Furthermore, they suggest that therapeutics to specifically increase or stabilize adult hippocampal neurogenesis could aid in preventing initial addiction as well as future relapse.
In the meantime, check out this show on sex addiction (it was on the Oprah Winfrey Show)!!!
Also, is hoarding an addiction? Check-out this episode on hoarders. Oprah thinks it is an addiction!
http://www.aetv.com/hoarders/video/?bcpid=44241147001&bclid=64070662001&bctid=74110546001
Think about it!
Peace,
–Sharonda
On Psychology and Neuroscience 
Wow, there is so much in this post! First, it is interesting to not that addicts tend to have a high tendency to relapse, maybe it has to do with their damaged cortex or maybe it has to do with their personality. Maybe they’re just weaker in general and more susceptible to becoming addicted. Also, the sex addiction topic on Oprah was really interesting as well. I kind of have a problem with those kind of shows though because I wonder how much they are passionate about becoming clean and how badly they want publicity. Finally, I think hoarding is an addiction if not a compulsion. Those houses were so appalling, I couldn’t believe the condition they were in. The things they kept seemed like ordinary garbage but to us but they were so afraid to throw them out! Incredible!
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I think the study you mention is incredible! I feel like we can keep coming back to hippocampal neurogenesis over and over again regardless of the topic–it is interesting to see that there can be a mediary area of sorts in the brain that can have such an impact on pathologies. very cool.
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I think it’s really interesting that neurogenesis can play a role in relapse, since there’s such an emphasis on the drug addiction reward-motivational pathway. Now that we’ve had our discussion about relapse in class, I guess this links closely to the conditioned place preference with the animal models. Perhaps the prevelance of relapse can be correlated to context and environment, because I find it hard to imagine that after 20 years of being sober, someone has a biological craving for the substance!
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