Tuesday, October 18, 2011

Music Improves Dopaminergic Neurotransmission: The Effect of Music on Blood Pressure Regulation

Sutoo, D., & Akiyama, K. (2004). "Music improves dopaminergic neurotransmission: demonstration based on the effect of music on blood pressure regulation." Brain Research (August 2004) 1016, 2: 255-262

The focuse of the study was on how music reduces blood pressure in different patients. Although specific mechanisms how music modifies the brain were not known, it still plays an important role in the regulation various symptoms of epilepsy, Parkinson's, senile dementia and attention deficit hyperactivity disorder.

Dopamine (DA) is a neurotransmitter involved in the increase and decrease of heart rate and blood pressure. Calmodulin (CaM) is a calcium-modulated protein that binds itself to calcium. It mediates activities such as metabolism, immunue system and intracellular movements. Previous studies have proved that calcium increases dopamine (DA) synthesis through a process called calmoduli(CaM)-dependent phosphorylation. The calcium ions are transported to the brain through blood: they enhance CaM activities and in return increase DA synthesis. The increase of dopaminergic activity further inhibits sympathetic nerve activities ("fight-or-flight" response), thus calming the blood pressure. (255-256)

The test subjects were spontaneously hypertensive (high blood pressure) rats. Mozrt's Adagio from Divertinento No.7 in D Major (K.205) was played repeatedly for 2 hours to the test group. Blood pressure levels were measured before, during, and after the experiement. The results were also compared to: 1. groups of rats with injections of various drugs targetted on dopamine and CaM receptors (W-7, SCH23390, EDTA, etc.), and 2. the non-music group of rats.
In the first group (music without injections), the blood pressure level in the rats decreased significantly within the 30 minutes of exposing to Mozart's music (approximately 190 to 170 mmHg). The effect continued to last, and reached its lowest point (165mmHg) even 30 minutes after the music finished. The blood pressure gradually returned back to normal after that duration.

Compared to the non-music group of almost no blood pressure changes, music was evident in the decrease of blood levels. To confirm whether the effect of music affected the calcium and DA synthesis, the rats with different injections were placed through the same music listening experiment. The results showed that the blood pressure levels from drugs that inhibited CaM, Calcium and Dopamine receptors (W-7, EDTA, Eticlopride, aMPT) showed no changes when exposed to the music. However, Dopamine (DA) type one (D1) receptor SCH23390 did not inhibit the music's ability to increase calcium levels, and that group of rats did have a decrease of blood pressure. This showed that the calcium passes through specific types of dopamine receptors (D2).

Neuroimaging has also provided more information on the region which DA levels were increased by the exposure to music. Only the laterial neostriatum region was shown with a heightened level of calcium after the music exposure. The study concluded with the findings and implications for further studies in music therapy.

As the introduction stated, "Music has a long history of healing physical and mental illnesses" (255). It is definitely interesting to see how the brain/body reacts to the mere sound of music. The study was done to three groups of rats and the results were compared. It is astonishing that even after the two-hour period, the blood pressure level continued to decrease. The continuing effect of music must have triggered parts in the brain that regulate short-term memory, so that even when the music is finished, the brain can still organize and process it to increase calcium levels.

The researchers stated that they do not know why and how music increases calcium levels, so that would be an interesting research to look into. It is curious that music listening evokes higher calcium levels in the lateral neostraium and nowhere else. It would be helpful to include some footnotes in the the study to examine keywords that are more biological.

It is also said that the increase of calcium/CaM in the DA synthesis process only passes through D2 receptors. Although no answers to why this happens, it is fascinating to see that everything in the brain is organized and categorized accroding to its various functions. I also would like to understand why the specific adagio from Mozart's Divertimento was chosen, and wheather certain elements in the music played a role in activation calcium levels.

In the last few paragraphs, the author talked about the similarity between music and exercise, and how exercise also stimulates the same pathway as the one illustrated in this experiment. This is important to use in combination to music therapy for better recovery as well. One topic to look further would be the effects of music on ADHD, epilepsy, dementia and Parkinson's disease in terms of regulating blood pressure level.

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