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The hormonal Zeitgeber melatonin: role as a circadian modulator in memory processing.

Rawashdeh O, Maronde E - Front Mol Neurosci (2012)

Bottom Line: Undoubtedly, however, melatonin plays an important role as a time cue for the endogenous circadian system.Memory processes (acquisition, consolidation, and retrieval) are modulated by the circadian system.However, the mechanism by which the biological clock is rhythmically influencing cognitive processes remains unknown.

View Article: PubMed Central - PubMed

Affiliation: Dr. Senckenbergische Anatomie III, Institute of Cellular and Molecular Anatomy, Goethe-University, Frankfurt Hessen, Germany.

ABSTRACT
The neuroendocrine substance melatonin is a hormone synthesized rhythmically by the pineal gland under the influence of the circadian system and alternating light/dark cycles. Melatonin has been shown to have broad applications, and consequently becoming a molecule of great controversy. Undoubtedly, however, melatonin plays an important role as a time cue for the endogenous circadian system. This review focuses on melatonin as a regulator in the circadian modulation of memory processing. Memory processes (acquisition, consolidation, and retrieval) are modulated by the circadian system. However, the mechanism by which the biological clock is rhythmically influencing cognitive processes remains unknown. We also discuss, how the circadian system by generating cycling melatonin levels can implant information about daytime into memory processing, depicted as day and nighttime differences in acquisition, memory consolidation and/or retrieval.

No MeSH data available.


Related in: MedlinePlus

Working model, illustrating the hypothesized rhythmic modulatory role of endogenous melatonin on memory processing. Cycling endogenous melatonin levels regulated by the circadian clock and by light/dark cycles, modulate the processing of newly acquired information into long-term memory. Inhibition (┤) of melatonin synthesis by the circadian clock or light directly, facilitates (►+) long-term memory formation. Alternatively, the nighttime peak in melatonin levels imposes an inhibitory effect (┤−) on memory consolidation.
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Figure 2: Working model, illustrating the hypothesized rhythmic modulatory role of endogenous melatonin on memory processing. Cycling endogenous melatonin levels regulated by the circadian clock and by light/dark cycles, modulate the processing of newly acquired information into long-term memory. Inhibition (┤) of melatonin synthesis by the circadian clock or light directly, facilitates (►+) long-term memory formation. Alternatively, the nighttime peak in melatonin levels imposes an inhibitory effect (┤−) on memory consolidation.

Mentions: To confirm that endogenous melatonin plays a role in the circadian modulation of memory performance, demanded the removal of the main source of melatonin synthesis, namely the pineal gland (Figure 1). The data show that pinealectomy per se has no effect on acquisition and on the improvement of daytime AAC performance during testing as compared to sham operated animals. In contrast to daytime memory performance for AAC, nighttime memory performance was different. During nighttime, when pinealectomized animals were trained for AAC, zebrafish demonstrate memory performance for AAC similar to their performances for normal daytime trained animals. Therefore, it was concluded that endogenous nighttime melatonin has an inhibitory effect on zebrafish nighttime AAC performance. Whether this effect of melatonin is species specific and/or dependent on the activity profile of the animal model (diurnal vs. nocturnal) remains to be investigated. However, in the case of zebrafish, we conclude that cycling physiological melatonin is one mechanism by which the circadian system is rhythmically modulating memory processing for AAC (Figure 2).


The hormonal Zeitgeber melatonin: role as a circadian modulator in memory processing.

Rawashdeh O, Maronde E - Front Mol Neurosci (2012)

Working model, illustrating the hypothesized rhythmic modulatory role of endogenous melatonin on memory processing. Cycling endogenous melatonin levels regulated by the circadian clock and by light/dark cycles, modulate the processing of newly acquired information into long-term memory. Inhibition (┤) of melatonin synthesis by the circadian clock or light directly, facilitates (►+) long-term memory formation. Alternatively, the nighttime peak in melatonin levels imposes an inhibitory effect (┤−) on memory consolidation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3295223&req=5

Figure 2: Working model, illustrating the hypothesized rhythmic modulatory role of endogenous melatonin on memory processing. Cycling endogenous melatonin levels regulated by the circadian clock and by light/dark cycles, modulate the processing of newly acquired information into long-term memory. Inhibition (┤) of melatonin synthesis by the circadian clock or light directly, facilitates (►+) long-term memory formation. Alternatively, the nighttime peak in melatonin levels imposes an inhibitory effect (┤−) on memory consolidation.
Mentions: To confirm that endogenous melatonin plays a role in the circadian modulation of memory performance, demanded the removal of the main source of melatonin synthesis, namely the pineal gland (Figure 1). The data show that pinealectomy per se has no effect on acquisition and on the improvement of daytime AAC performance during testing as compared to sham operated animals. In contrast to daytime memory performance for AAC, nighttime memory performance was different. During nighttime, when pinealectomized animals were trained for AAC, zebrafish demonstrate memory performance for AAC similar to their performances for normal daytime trained animals. Therefore, it was concluded that endogenous nighttime melatonin has an inhibitory effect on zebrafish nighttime AAC performance. Whether this effect of melatonin is species specific and/or dependent on the activity profile of the animal model (diurnal vs. nocturnal) remains to be investigated. However, in the case of zebrafish, we conclude that cycling physiological melatonin is one mechanism by which the circadian system is rhythmically modulating memory processing for AAC (Figure 2).

Bottom Line: Undoubtedly, however, melatonin plays an important role as a time cue for the endogenous circadian system.Memory processes (acquisition, consolidation, and retrieval) are modulated by the circadian system.However, the mechanism by which the biological clock is rhythmically influencing cognitive processes remains unknown.

View Article: PubMed Central - PubMed

Affiliation: Dr. Senckenbergische Anatomie III, Institute of Cellular and Molecular Anatomy, Goethe-University, Frankfurt Hessen, Germany.

ABSTRACT
The neuroendocrine substance melatonin is a hormone synthesized rhythmically by the pineal gland under the influence of the circadian system and alternating light/dark cycles. Melatonin has been shown to have broad applications, and consequently becoming a molecule of great controversy. Undoubtedly, however, melatonin plays an important role as a time cue for the endogenous circadian system. This review focuses on melatonin as a regulator in the circadian modulation of memory processing. Memory processes (acquisition, consolidation, and retrieval) are modulated by the circadian system. However, the mechanism by which the biological clock is rhythmically influencing cognitive processes remains unknown. We also discuss, how the circadian system by generating cycling melatonin levels can implant information about daytime into memory processing, depicted as day and nighttime differences in acquisition, memory consolidation and/or retrieval.

No MeSH data available.


Related in: MedlinePlus