Induction of a torpor-like hypothermic and hypometabolic state in rodents by ultrasound
Torpor is an energy-conserving state in which animals dramatically decrease their metabolic rate and body temperature to survive harsh environmental conditions. Here, we report the noninvasive, precise, and safe induction of a torpor-like hypothermic and hypometabolic state in rodents by remote transcranial ultrasound stimulation at the hypothalamus preoptic area (POA). We achieve a long-lasting (> 24 hours) torpor-like state in mice via closed-loop feedback control of ultrasound stimulation with automated detection of body temperature. Ultrasound-induced hypothermia and hypometabolism (UIH) is triggered by activation of POA neurons, involves the dorsomedial hypothalamus as a downstream brain region and subsequent inhibition of thermogenic brown adipose tissue. Single-nucleus RNA-sequencing of POA neurons reveals TRPM2 as an ultrasound-sensitive ion channel, the knockdown of which suppresses UIH. We also demonstrate that UIH is feasible in a non-torpid animal, the rat. Our findings establish UIH as a promising technology for the noninvasive and safe induction of a torpor-like state. To investigate the mechanism of ultrasound-induced neuronal activation, we applied ultrasound stimulation in hypothalamic preoptic area region and performed single-nuclei RNA sequencing in the ultrasound stimulated neurons (US+) and neurons without ultrasound stimulation (US-). In our sn-RNAseq analysis, we examined the association between the expression of neuronal activation markers (or IEGs) and ion channels, as well as neuron types. Overall design: The hypothalamic preoptic area from ultrasound-stimulated (US+) and sham (CON, US-) groups, involving 4 mice per group.  Brain tissues were dissected approximately 1 hour after ultrasound stimulation.