A discrete neuronal circuit induces a hibernation-like state in rodents.

Hibernating mammals actively lower their body temperature to reduce energy expenditure when facing food scarcity1. This ability to induce a hypometabolic state has evoked great interest owing to its potential medical benefits2,3. Here we show that a hypothalamic neuronal circuit in rodents induces a long-lasting hypothermic and hypometabolic state similar to hibernation. In this state, although body temperature and levels of oxygen consumption are kept very low, the ability to regulate metabolism still remains functional, as in hibernation4. There was no obvious damage to tissues and organs or abnormalities in behaviour after recovery from this state. Our findings could enable the development of a method to induce a hibernation-like state, which would have potential applications in non-hibernating mammalian species including humans.

Capturing and Manipulating Activated Neuronal Ensembles with CANE Delineates a Hypothalamic Social-Fear Circuit.

We developed a technology (capturing activated neuronal ensembles [CANE]) to label, manipulate, and transsynaptically trace neural circuits that are transiently activated in behavioral contexts with high efficiency and temporal precision. CANE consists of a knockin mouse and engineered viruses designed to specifically infect activated neurons. Using CANE, we selectively labeled neurons that were activated by either fearful or aggressive social encounters in a hypothalamic subnucleus previously known as a locus for aggression, and discovered that social-fear and aggression neurons are intermixed but largely distinct. Optogenetic stimulation of CANE-captured social-fear neurons (SFNs) is sufficient to evoke fear-like behaviors in normal social contexts, whereas silencing SFNs resulted in reduced social avoidance. CANE-based mapping of axonal projections and presynaptic inputs to SFNs further revealed a highly distributed and recurrent neural network. CANE is a broadly applicable technology for dissecting causality and connectivity of spatially intermingled but functionally distinct ensembles.

Simultaneous observation of the GnRH pulse generator activity and plasma concentrations of metabolites and insulin during fasting and subsequent refeeding periods in Shiba goats.

The time course of GnRH pulse generator activity and plasma concentrations of energy substrates and insulin were simultaneously observed in female goats during 4-day fasting and subsequent refeeding in the presence or absence of estrogen for a better understanding of the mechanism of energetic control of gonadotropin secretion in ruminants. The GnRH pulse generator activity was electrophysiologically assessed with the intervals of characteristic increases in multiple-unit activity (MUA volleys) in the mediobasal hypothalamus. In estradiol-treated ovariectomized (OVX+E2) goats, the MUA volley intervals increased as fasting progressed. Plasma concentrations of non-esterified fatty acid and ketone body increased, while those of acetic acid and insulin decreased during fasting. The MUA volley intervals and plasma concentrations of those metabolites and insulin were restored to pre-fasting levels after subsequent refeeding. In ovariectomized (OVX) goats, changes in plasma metabolites and insulin concentrations were similar to those in OVX+E2 goats, but the MUA volley intervals were not altered. The present results demonstrated that fasting suppressed GnRH pulse generator activity in an estrogen-dependent manner. Changes in plasma concentrations of energy substrates and insulin during fasting were associated with the GnRH pulse generator activity in the presence of estrogen, but not in the absence of the steroid in female goats.