Dopamine is the neurotransmitter that is responsible for many physiological responses that include pathology and feelings of excitement. Dopamine is generally released in response to stimuli. An example of such a release is through events such as roller coaster acceleration, or eating sugary food, both of which trigger the release of dopamine which conveys feelings of excitement. There are other methods of releasing dopamine exogenously such as consuming drugs that are precursors to this neurotransmitter.
In his article “Challenges to Body Fluid Homeostasis Differentially Recruit Phasic Dopamine Signaling in a Taste-Selective Manner”, Dr. Roitman explained the how the presents of salts specifically can modulate the levels of dopamine released in our nervous system. His studies were with rats, and his findings indicated that upon a forced sodium depletion diet, there was a significant increase in the level of dopamine released in the nervous system. Figure 3b, in his paper specifically highlights this finding. This is interesting, because his research is exploring a sort of dynamic dopamine system that is able to change in accordance with its environment, such as the exposure of salt in our diets. A similar dynamic dopamine system was found in rats recently by a paper published just a few months earlier. In the article “Operant Costs Modulate Dopamine Release to Self-Administered Cocaine”, Dr. Wanat and Dr. Olivia explore the levels of dopamine present in the ventral medial striatum in rats. This is related to Dr. Roitman’s research because this new finding with cocaine indicated that operant costs affect reward-evoked dopamine release in the VMS of rats.
The findings of Dr. Wanat and Dr. Olivia are related to Dr. Roitman’s findings, because this research also shows dynamic levels of phasic dopamine in our nervous system. In this paper specifically, they measure the levels of dopamine present in the ventral medial striatum (VMS). Their findings indicate that upon self-administration of dopamine via cocaine, levels of dopamine were shown to increase when the operant requirement is lowered. What this means is when the mice had to work hard to obtain cocaine and thus dopamine, their levels of dopamine present in the VMS were significantly lower compared to when the mice had a lower cost related to the acquisition of cocaine.
Another interesting finding in this research article by Dr. Wanat and Dr. Olivia was that increasing the time before the presentation of the reward can increase the levels of dopamine in the VMS. It is important to remember that they measured these levels of dopamine in the VMS via singe-cell unit recordings. Their findings indicate that the mere anticipation for a reward, such as food, can lead to an increased level of dopamine bioavailability in our nervous system. “Increasing the delay before juice/food rewards are delivered in a larger reward-evoked dopamine response”.
Both the findings of Dr. Roitman in his paper and Dr. Wanat & Olivia in their paper indicate that the system that regulates dopamine in our nervous system is not static, but rather dynamic. The levels of dopamine in our nervous system can be modulated by exogenous factors such as environmental stimuli that include food that we eat, and the effort exerted to obtain reward-based things.
In the discussion portion of this paper, they discuss a very significant topic, addiction. Cocaine addiction is very deadly, and it is an addiction that is very hard to give up. This paper sheds light upon that concept, because their research indicates that when the cost of obtaining reward-evoking stimuli is low, then the level of dopamine release is substantially higher. In cocaine addicts, there ease of access to the drug may cause higher levels of physiological response therefore solidifying the extent of their addiction and making it harder to quit.
In conclusion, I think it is important to consider the dynamic abilities of our neural system that regulate dopamine when conducting further research upon these subcortical systems. As the speaker illustrated in class, and as this paper has shown, levels of dopamine are highly dependent upon the stimuli that we are exposed to. This leads us to more questions. Are there other variables that may affect the regulation of dopamine in our nervous system?
Article“Operant Costs Modulate Dopamine Release to Self-Administered Cocaine”
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