Explain the role of the neurotransmitter dopamine in the development of substance use disorder. With reference to instrumental conditioning, how does dopamine support initial drug taking?

In the stages leading to the development of a substance use disorder, dopamine plays a large role in the likeliness for future administration of the substance through feelings of satisfaction and pleasantness. Voluntary actions and factors actuated by the user prior to administration further contribute to a development of substance use disorder, by means of instrumental conditioning.

Through the administration of substances, changed levels of dopamine affect the satisfaction and overall liking of the substance. Dopamine neurotransmitters exist throughout the human body, carrying chemical signals between the body and the brain, inclusive of signals relevant to feelings of pleasure. Substances - by nature - modify the levels of various neurotransmitters in the body to elicit a specific outcome. In substances that modify dopamine levels, they alter the body's functions to ultimately absorb more dopamine. For example, with the administration of cocaine, the body's natural reuptake of excess dopamine neurotransmitters is blocked, causing more dopamine to be absorbed. Furthermore, the administration of amphetamine-type substances causes a greater release of dopamine neurotransmitters from the vesicles that they are stored in, which also causes more dopamine to be absorbed. Consequently, increased levels of dopamine in the body have the potential to affect the user's perception of their experience as being more pleasurable. This may encourage the user to administer the substance again, in the pursuit of feeling happy, which may exacerbate the potent effects of the substance. As such, dopamine neurotransmitters play a primary role in the development of substance use disorders, as the change in their levels affect the satisfaction and liking of that substance.

Whilst dopamine levels can be affected through the ingredients in the substance, voluntary actions and voluntary environmental factors can too affect levels of dopamine, which too influence the liking of the substance and lead to possible developments of substance use disorders. Instrumental conditioning (also known as operant conditioning) is a learning framework whose end results associate a voluntary action with an expected reward - whether it be tangible or intangible. Instrumental conditioning is not limited to only the mind, by nature of the brain linking an action to a reward, but also extensible towards the body's subconscious and autonomous functions itself. In light of substance use, if an individual regularly performs a set of voluntary actions, or places themself in an environment voluntarily, their body may be subconsciously conditioned to elicit a response. The body may associate voluntary actions with the aforementioned effects and implications of inflated dopamine levels, which can result in autonomous bodily reactions occurring when in that environment, even without the presence of the substance. Consequently, dopamine too plays a large role in the instrumental conditioning of drug-like responses, whereby dopamine aids the associative process between a voluntary action or environment and a response, causing the body to produce a similar reaction when faced with that action or environment.

Explain how changes in the functioning of the dopamine system lead to the development of withdrawal after drug use is ceased. With reference to instrumental conditioning, how does withdrawal contribute to ongoing drug use and relapse?

In the absence of once-regular administration, the development of withdrawal effects can be highly attributed as an effect of the body's overcompensation of functionality in its dopamine system. Additionally, as a result of possibly prior instrumental conditioning, voluntary actions and environments exhibit a tendency to lead a user to a state of withdrawal and possible relapse. During prolonged use of dopamine-affecting substances, in an attempt to reach an inertial state of chemical balance, the body attempts to regulate its effects by increasing or decreasing the activity of the body's functions. Receptor desensitisation deactivates a selection of receptors of the body's cell membrane, effectively reducing the number of absorbed dopamine neurotransmitters. Akin to this, down regulation kills receptor cells to also reduce the number of absorbed dopamine neurotransmitters. However, upon the removal or absence of the once-regular dosages of the substance, the body will continue to still operate in a compensating manner of reduced performance (having less active receptor cells until they activate or grow back), absorbing less of the dopamine neurotransmitters from the expected excess amount. Subsequently, without the presence of the expected excess amount of dopamine, the body instead absorbs fewer than usual amounts of dopamine, which may be inadequate or unsatisfactory for normal bodily operation. Whilst the number of active receptors is recoverable, the recovery process is slow, and will not lead to a full recovery (Foulds, 1996).

Consequently, users may enter a state of withdrawal where they exhibit effects opposite to what the substance provided. Were for a substance to be administered under the same voluntary actions and voluntary environments over a period of time, a user may exhibit involuntary bodily responses as a result of instrumental conditioning. Should these factors be experienced when the user is not under the influence of the substance, the involuntary conditioned response may induce elevated levels of withdrawal. Given previous positive experiences and peak highs (Foulds, 1996) when under the effects of the substance we, a user may feel compelled to take the substance once again, and enter a period of relapse. The Hazelden Betty Ford Foundation Butler Center For Research posits that "the intensified dopamine response in the brain that mood-altering drugs produce does not naturally stop" (Ranes et al. 2016). This agrees with the notion that substances have long-lasting effects even whilst a new dose of the substance may be absent and extends to involuntarily bodily behaviour and responses. Therefore, prolonged use of substance creates semi-permanent changes in the body's absorption mechanism, that when a user is no longer under active influence of the substance, he or she will result in a deprivation of dopamine and other affected neurotransmitters. In addition, actions and environments that may be conditioned stimuli as a result of operant conditioning can induce involuntary bodily response behaviours which may exacerbate the body's deprived state from overcompensated regulation, contributing to behaviours of relapse.

Discuss how drug-associated environmental cues can contribute to ongoing substance use and relapse. Hint: You may choose to approach this from the perspective of positive or negative reinforcement theories of addiction.

Chemical effects of substances on the brain and the body influence decisions and preferences, and are affected by both classical and instrumental conditioning. Compared to the voluntary nature of instrumental conditioning, classical conditioning dictates an induced behaviour as a result of an auxiliary stimulant such as a sound or visible object. Regardless of the type of conditioning framework, environmental cues such as sounds and locations can act as conditioned stimulants to elicit a conditioned response. These responses can include the desire to administer a substance, or the previously mentioned autonomous bodily responses. It is widely accepted that dopamine is responsible in the process of decision making, where the option with the greatest reward is favoured (Schults et al. 2002). Hence should either response occur, the conditioned body will favour the decision to consume the substance as it will provide the greatest pleasure and or relief.

In application of the positive reinforcement theory, the administration of substances to elevate a user's feelings makes the substance a rewarding choice. In application of negative reinforcement, the use of substances to provide elevated comfort or to mitigate symptoms of withdrawal favour substance use as highly rewarding. Furthermore, involuntary bodily responses may induce a desire or craving for feelings provided by the substance. Therefore, the chronic use of substances as well as stages of relapse can be attributed to the effects of long-term conditioning. Weaning out of substance abuse and episodes of relapse is difficult as even simple environmental cues can trigger involuntary behaviours and responses.

References

Foulds, J. (1996). Cognitive performance effects of subcutaneous nicotine in smokers and never-smoker. Psychopharmacology 1996;127 31-36

Ranes, B. (2016). Drug Abuse, Dopamine, and the Brain’s Reward System. Hazelden Betty Ford Foundation Butler Center For Research

Schultz, W. (2002). Getting formal with dopamine and reward. Neuron 2002;36 (2) 241- 263

Volkow ND, Fowler JS, Wang G, Swanson JM, Telang F. Dopamine in Drug Abuse and Addiction: Results of Imaging Studies and Treatment Implications. Arch Neurol. 2007;64(11):1575–1579. doi:10.1001/archneur.64.11.1575

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Heh welllllllllllllll I ain't a scientist. Scientific writing go brrr