Sometimes we just can’t say no. From first try to habit, it’s all chemistry. Charlotte Steward takes a look at the ups and downs of chemical addiction. enjoy a drug to become addicted to it. Hedonics is the division of psychology that deals with this pleasurable or unpleasurable state of consciousness. It demonstrates that the ‘liking’ and ‘wanting’ parts of our brain are separate, which explains why we might want a drug without actually enjoying it. This is the reason why nicotine in cigarettes is highly addictive compared to other substances despite its lower euphoric rewards. Drugs are not equal in their addiction potential. In general, the quicker the drug reaches the brain, the more addictive it is. The rate at which a drug reaches the brain is important because drugs cause changes in gene expression. Neural plasticity is the brain’s ability to form and break connections between neurons, allowing it to adjust its activity in response to new circumstances and changes in the environment. Faster acting drugs affect ‘immediate-early gene’ expression, which is central to encoding memories through neural plasticity.
a potential addiction therapy. When a drug is delivered through the skin or by ingestion, a longer-lasting and weaker effect is produced. This reduces patients’ withdrawal symptoms as the drug stabilises the brain and is less addictive. This idea is becoming increasingly popular as a potential treatment option – a common example being the nicotine patch.
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Different methods of delivery can have an effect on the potency of a drug by varying the rate at which it reaches the brain. The fastest route to the brain is by smoking, followed by injection, snorting, and then ingestion. For example, alcohol takes a few minutes to cause biological and behavioural changes compared to the mere seconds taken by more addictive drugs. As addiction progresses, users who become more reliant on drugs often change their method of delivery in favour of more immediate and intense highs. However, there are several other factors to addition that can affect the addiction potential of a drug. What does this mean for treatment options? We can use our knowledge of slow delivery as
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Recent experiments have shown that it is possible to reverse drug-induced changes in the brain.
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Recent experiments have shown that it is possible to reverse drug-induced changes in the brain. Neuroscience research has set out to reverse the changes to synapses that have been strengthened by drug use, essentially resetting the wiring of the brain to a non-addicted state. This approach uses optogenetics, a technique that allows modified neurons to become activated by light rather than a chemical trigger. It is not currently possible to genetically modify humans, so for the time being this remains a proof of principle rather than a miracle cure.
phenomenon. Select sub-groups in many species have been proven to be highly impulsive while others show an elevated responsiveness to novelty. The ‘sensation seeking’ personality trait is identified in people who are willing to take legal, social, financial, and physical risks for experiences and feelings that are varied, novel, complex, and intense. The increased responsiveness to novelty in this sub-group has also been shown to increase the chances of initiating drug use. While ‘sensation seekers’ are more likely to initiate drug use, those who are highly impulsive are more likely to develop an ongoing addictive behaviour. Analysis of the compulsive nature of drug taking in ‘impulsive’ groups suggests that these individuals had neurons in the prefrontal cortex – an area at the front of the brain – that were less active than normal. As the prefrontal cortex is largely responsible for anticipating negative consequences and managing selfcontrol, people with decreased activity in this area are more likely to make rash decisions and have less control over their behaviour. This characteristic allows them to largely disregard any potential aversive outcomes, thus enabling them to continually self-administer even when it is destructive to do so.
While some drugs are more addictive than others, are some people more susceptible to addiction? To what extent do familial traits dictate our vulnerability, and how may we overcome this?
Addictive drugs increase the amount of dopamine in the brain, triggering our reward prediction system. As the neurochemical mechanism to control hunger also modifies dopamine neuron activity, this raises the question – might it be possible to become addicted to more common substances such as food? This research is well underway and findings to date suggest that it is very likely.
DNA may predispose some people to addiction, as explained by the ‘addictive personality’
Charlotte Steward is studying for a BSc in Biochemistry
I, Science
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