Primary Research · 2015
The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus
Kawai N, Sakai N, Okuro M, et al. · Neuropsychopharmacology, 2015
Key finding
Mechanistic study identifying how glycine at bedtime lowers core body temperature via NMDA receptor activation in the SCN — the proposed mechanism for its observed sleep-onset latency benefits.
Abstract
PubMed · PMID 25533534 →The use of glycine as a therapeutic option for improving sleep quality is a novel and safe approach. However, despite clinical evidence of its efficacy, the details of its mechanism remain poorly understood. In this study, we investigated the site of action and sleep-promoting mechanisms of glycine in rats. In acute sleep disturbance, oral administration of glycine-induced non-rapid eye movement (REM) sleep and shortened NREM sleep latency with a simultaneous decrease in core temperature. Oral and intracerebroventricular injection of glycine elevated cutaneous blood flow (CBF) at the plantar surface in a dose-dependent manner, resulting in heat loss. Pretreatment with N-methyl-D-aspartate (NMDA) receptor antagonists AP5 and CGP78608 but not the glycine receptor antagonist strychnine inhibited the CBF increase caused by glycine injection into the brain. Induction of c-Fos expression was observed in the hypothalamic nuclei, including the medial preoptic area (MPO) and the suprachiasmatic nucleus (SCN) shell after glycine administration. Bilateral microinjection of glycine into the SCN elevated CBF in a dose-dependent manner, whereas no effect was observed when glycine was injected into the MPO and dorsal subparaventricular zone. In addition, microinjection of D-serine into the SCN also increased CBF, whereas these effects were blocked in the presence of L-701324. SCN ablation completely abolished the sleep-promoting and hypothermic effects of glycine. These data suggest that exogenous glycine promotes sleep via peripheral vasodilatation through the activation of NMDA receptors in the SCN shell.
Abstract sourced from PubMed, a database of the U.S. National Library of Medicine. Displayed in the authors’ own words for context; our critique is in the sections below.
About the supplement
Glycine
Dose · mechanism · evidence grade · safety →
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