MELATONIN IN THE NEWS

A recent study published in NeuroReport titled Effects of melatonin on phosphorylation of memory-related proteins in the hippocampus and the perirhinal cortex in male mice has news outlets taking notice. The researchers of this study have contributed to helping explain the mechanism of how melatonin impacts memory.

 

This animal study aimed to investigate how melatonin (the hormone secreted from the pineal gland), ramelteon (a drug that binds and activates melatonin receptors), and AMK (melatonin’s biological metabolite) impacted phosphorylation of memory-related proteins. Phosphorylation is the addition of a phosphate group to a molecule and is a critical process needed for cells and the regulation of protein function.

 

In this study, the phosphorylation of five protein associated with memory were explored:

1. Extracellular signal-regulated kinase (ERK)

2. Calcium/calmodulin-dependent kinase IIα (CaMKIIα)

3. Calcium/calmodulin-dependent kinase IIβ (CaMKIIβ)

4. Calcium/calmodulin-dependent protein kinase IV (CaMKIV)

5. cAMP-response element binding protein (CREB)

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Highlights of the study design include:

• Male mice were assessed using NORT --novel objection recognition task experimentation.

• The mice were exposed to 12 hours of light and 12 hours of dark.

• After the initial memory test, a single administration of melatonin, ramelteon, or AMK was given (1 mg/kg) and compared against a control.

• Female mice were not tested due to the impact the reproductive cycle may have on results.

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Results

Experiment 1: The recognition of a novel object was significantly increased in all three treated groups compared to the control group, suggesting the promotion of long-term memory formation.  

• Melatonin: P< 0.001

• Ramelteon: P<0.001

• AMK: P<0.01

Experiment 2: After euthanasia, the researchers sampled the mice’s brains to look at the phosphorylation of proteins found in the hippocampus and perirhinal cortex (The two areas where memories are formed.)