Investigate the mechanisms of anesthetic-induced unconsciousness in a mouse model by high-resolution manganese enhanced MRI (MEMRI) technique: A Preliminary Study

INTRODUCTION: Manganese is a useful contrast agent for MRI of animals [1], which utilizes the fact that paramagnetic manganese ions (Mn) enter synaptically activated neurons through voltage-gated calcium channels [2], resulting in enhancement on T1-weighted MRI images. Although much progress has been made deciphering the effects of anesthetics upon individual ion channels, we are only beginning to identify putative neural substrates upon which anesthetics act to produce their behavioral effects. Of the key components that characterize the anesthetized state, we focus on volatile anesthetic-induced unconsciousness, defined as a lack of perceptive awareness to non-noxious stimuli. Two emerging hypothalamic targets with proven ability to affect arousal state are the median preoptic nucleus, MnPO, and ventrolateral preoptic nucleus, VLPO. Depolarization of these two regions is respectively thought to underlie onset and maintenance of natural sleep. Our hypothesis is that volatile anesthetics cause unconsciousness (behavioral hypnosis) by affecting VLPO and MnPO function. In this preliminary study, we verified the hypothesis by highresolution MEMRI technique, the results showed clear signal enhancements within MnPO of the anesthetized mice compared to the awake control.