MT2

The melatonin MT2 receptor (MT₂) is a high-affinity G protein-coupled receptor that mediates melatonin’s effects on circadian rhythm regulation and sleep architecture^[1][2]. Mechanistically, MT₂ activation modulates intracellular cAMP, Ca²⁺ signaling, and downstream kinases including CaMKII and ERK, thereby influencing neuronal excitability and synaptic plasticity^[3][4][5]. Compared with MT1 receptors, MT₂ exhibits distinct localization in the reticular thalamus and hippocampus, favoring non-REM sleep modulation and anxiolytic-like effects^[2][6][7]. In neuropathic pain models, MT₂ agonists such as IIK-7 and UCM924 reduce mechanical allodynia, suppress spinal microglial activation, and engage descending brainstem antinociceptive circuits via opioid-dependent mechanisms^{[8][9][10][11]}. MT₂ also contributes to neuroprotection, as activation prevents Aβ-induced dendritic impairments and attenuates oxidative stress in hippocampal neurons, partially via the cAMP-C/EBPα/miR-125b and ERK/Nrf2 pathways^[12][5]. Selective MT₂ ligands display isoform-specific pharmacology, acting as full or partial agonists, enabling targeted experimental modulation without affecting MT1-mediated REM sleep pathways^[13][2]. These properties support MT₂ as a distinct therapeutic target in sleep, neurodegenerative disorders, pain, and oxidative stress-related conditions, with well-characterized signaling profiles for research applications^[1][3][11].