The Pineal Gland and Melatonin
The theory goes that turkey contains high levels of tryptophan, which is a key ingredient of serotonin and melatonin; the tryptophan in the turkey. Serotonin and melatonin are both hormones that regulate various human functions such as sleep, appetite and mood. Low serotonin levels, on the other hand, are linked to weakened immune function and depression. It is produced in the pineal gland in the brain when it's dark outside. Relationship between nocturnal serotonin surge and melatonin onset in We have recently reported dynamic circadian rhythms of serotonin.
Summary Tryptophan is an amino acid that can be converted into several important molecules, including serotonin and melatonin. Tryptophan and the molecules it produces influence many functions in the body, including sleep, mood and behavior. Although tryptophan has many functions, its impact on the brain is particularly notable. Low Levels Are Associated With Mood Disorders Several studies have shown that those experiencing depression may have tryptophan levels that are lower than normal 78.
Other research has examined the effects of altering blood levels of tryptophan.
By lowering tryptophan levels, researchers can learn about its functions. To do so, study participants consume large amounts of amino acids, with or without tryptophan 9.
One such study exposed 15 healthy adults to a stressful environment twice — once when they had normal tryptophan blood levels and once when they had low levels The researchers found that anxiety, tension and feelings of nervousness were higher when the participants had low tryptophan levels.
Based on these results, low levels of tryptophan could contribute to anxiety They may also increase aggression and impulsiveness in aggressive individuals On the other hand, supplementing with tryptophan may promote good social behavior Summary Research has shown that low levels of tryptophan may contribute to mood disorders, including depression and anxiety. One study found that when tryptophan levels were lowered, long-term memory performance was worse than when levels were normal These effects were seen regardless of whether the participants had a family history of depression.
Additionally, a large review found that lower tryptophan levels negatively impacted cognition and memory Memory linked to events and experiences may be particularly impaired.
These effects are likely due to the fact that as tryptophan levels are lowered, serotonin production decreases Summary Tryptophan is important for cognitive processes because of its role in serotonin production. Low levels of this amino acid can impair your cognition, including your memory of events or experiences.
Based on numerous experiments, researchers agree that many of the effects of high or low tryptophan levels are due to its effects on serotonin or 5-HTP In other words, increasing its levels can lead to increased 5-HTP and serotonin 17 Serotonin and 5-HTP affect many processes in the brain, and interference with their normal actions may impact depression and anxiety 5.
Relationship between nocturnal serotonin surge and melatonin onset in rodent pineal gland
In fact, many drugs designed to treat depression modify the action of serotonin in the brain to increase its activity Treatment with 5-HTP can also help increase serotonin and improve mood and panic disorders, as well as insomnia 5 Overall, the conversion of tryptophan to serotonin is responsible for many of its observed effects on mood and cognition Summary The importance of tryptophan is likely due to its role in serotonin production.
Serotonin is essential for the proper functioning of the brain, and low tryptophan levels reduce the amount of serotonin in the body. Impact on Melatonin and Sleep Once serotonin has been produced from tryptophan in the body, it can be converted into another important molecule — melatonin. In fact, research has shown that increasing tryptophan in the blood directly increases both serotonin and melatonin In addition to being found naturally in the body, melatonin is a popular supplement and found in several foods, including tomatoes, strawberries and grapes Melatonin influences the sleep-wake cycle of the body.
- Relationship between nocturnal serotonin surge and melatonin onset in rodent pineal gland
- Serotonin Vs. Melatonin
- How Tryptophan Boosts Your Sleep Quality and Mood
This cycle impacts many other functions, including the metabolism of nutrients and your immune system Several studies have shown that increasing tryptophan in the diet can improve sleep by increasing melatonin 24 One study found that eating tryptophan-enriched cereal at breakfast and dinner helped adults fall asleep faster and sleep longer, compared to when they ate standard cereals Symptoms of anxiety and depression were also reduced, and it is likely that the tryptophan helped increase both serotonin and melatonin.
Other studies have also shown that taking melatonin as a supplement can improve sleep quantity and quality 26 Increasing tryptophan intake can lead to higher levels of melatonin and may improve sleep quantity and quality. Many different protein-containing foods are good sources of tryptophan Because of this, you get some of this amino acid almost any time you eat protein. Your intake depends on how much protein you consume and which protein sources you eat.
Some foods are particularly high in tryptophan, including poultry, shrimp, eggs, elk and crab, among others It has been estimated that a typical diet provides approximately 1 gram per day In contrast, 5HT-on of hamsters led MT-on by as much as min. Thus, while a constant relationship of 5HT-on and MT-on exists for animals of the same species, the relative timings of 5HT-on and MT-on differ between animals of different species. Conclusion These results suggest that both 5-HT and melatonin could serve as reliable markers of the circadian clock because of their day-to-day precision of onset timings within the same animals or within individuals of the same strain or same species.The Relationship between Dopamine and Melatonin
The results also demonstrate that data for MT-on cannot be compared directly between different species, and that 5HT-on may be a more reliable circadian marker when data from animals of different species are compared.
Background Circadian rhythm studies have utilized the onset phases of rhythmic outputs, such as locomotor activities of laboratory rodents [ 1 ], temperature, and melatonin secretion [ 23 ], as markers of the circadian clock.
The reliability and consistency of these circadian output markers are essential for an accurate pacemaker analysis across multiple circadian cycles of the same individuals, between different individuals of the same animal strain, between different strains of the same animal species, and between individuals of different species [ 4 ].
This study analyzes circadian characteristics of pineal 5-HT and melatonin secretion in rats and hamsters under entrained conditions. The pineal gland of all vertebrate animals produces melatonin from 5-HT in response to the norepinephrine released from the superior cervical ganglion SCG [ 56 ]. The production and secretion of 5-HT and melatonin are regulated by the circadian clock situated in the suprachiasmatic nuclei, and are elevated at night in rats [ 7 ]. Because of the tight association of pineal melatonin release with the clock activity, melatonin has been regarded as an accurate marker of the circadian pacemaker for both animal and human circadian rhythm studies [ 8 - 12 ].
In human studies, for example, the onset timing of melatonin release at night has been used extensively to determine the phase angle of circadian pacemaker entrainment [ 13 ]. Comparative analysis of MT-on from different individuals is conducted routinely in human studies, which is linked to circadian traits such as morningness and eveningness [ 13 ].
Melatonin vs. serotonin: the science behind a good night’s sleep
Such analyses are largely missing from animal studies for inter-cycle, inter-individual, inter-strain, and inter-species differences of MT-on. This is due to difficulties with high-resolution sampling and analysis of melatonin in small laboratory rodents using conventional methods. These difficulties are now overcome with our pineal microdialysis technique, which allows high-resolution analysis of pineal melatonin secretion in individual animals for extended periods in real time [ 23714 ].
Using this technique, this study is designed to provide detailed profiles of 5-HT and melatonin release under entrained conditions in rodents. Pineal melatonin is produced at night from 5-HT, which is synthesized within the pineal gland and displays dynamic circadian rhythms of both synthesis and release [ 7 ].
Unlike melatonin, whose synthesis in rodents requires transcriptional activation of the key enzyme serotonin N-acetyltransferase [ 15 ], the nocturnal surge of 5-HT production and release is controlled posttranscriptionally in the pineal gland [ 7 ]. Earlier data indicate that both synthesis and release of 5-HT are triggered by norepinephrine released from the SCG nerve terminals [ 7 ].
Compared to the lag time of about 1 h for melatonin output, there appears to be a minimum delay for 5-HT release when norepinephrine is directly infused into the pineal gland via microdialysis tubing [ 714 ]. These data indicate that the surge of 5-HT release in the night pineal gland broadcasts the timing of norepinephrine release from the SCG and, hence, the arrival timing of central circadian clock signals.
Initiation of melatonin production, however, could depend on pineal mechanisms downstream of the 5-HT surge, which could differ between individual animals of the same strain, be unique to each strain of rats, or be specific to different species of animals.
In this paper, secretion profiles of 5-HT and their relationship with melatonin are studied across multiple circadian cycles in multiple animals of the same strains, in multiple outbred as well as inbred strains of rats, and in both rats and hamsters.
Methods Animals Adult 2—4 months male animals of several strains of outbred and inbred rats, and outbred hamsters were analyzed in this study. The transgenic Wistar rats are kindly provided by Dr. Animals were housed in a temperature-controlled chamber with a light and dark LD cycle of Prior to on-line analysis of 5-HT and melatonin, animals were implanted with microdialysis probes directly in their pineal glands as described [ 14 ], and allowed to recover for 1—3 days.
Following recovery, animals were transferred to the dialysis chamber into their individual cages. The dialysis chamber was temperature-controlled, ventilated, and light proof.