Regulation of Energy Expenditure by Brainstem GABA Neurons.

Homeostatic control of core body temperature is essential for survival. Temperature is sensed by specific neurons, in turn eliciting both behavioral (i.e., locomotion) and physiologic (i.e., thermogenesis, vasodilatation) responses. Here, we report that a population of GABAergic (Vgat-expressing) neurons in the dorsolateral portion of the dorsal raphe nucleus (DRN), hereafter DRNVgat neurons, are activated by ambient heat and bidirectionally regulate energy expenditure through changes in both thermogenesis and locomotion. We find that DRNVgat neurons innervate brown fat via a descending projection to the raphe pallidus (RPa). These neurons also densely innervate ascending targets implicated in the central regulation of energy expenditure, including the hypothalamus and extended amygdala. Optogenetic stimulation of different projection targets reveals that DRNVgat neurons are capable of regulating thermogenesis through both a "direct" descending pathway through the RPa and multiple "indirect" ascending pathways. This work establishes a key regulatory role for DRNVgat neurons in controlling energy expenditure.

iDISCO: a simple, rapid method to immunolabel large tissue samples for volume imaging.

The visualization of molecularly labeled structures within large intact tissues in three dimensions is an area of intense focus. We describe a simple, rapid, and inexpensive method, iDISCO, that permits whole-mount immunolabeling with volume imaging of large cleared samples ranging from perinatal mouse embryos to adult organs, such as brains or kidneys. iDISCO is modeled on classical histology techniques, facilitating translation of section staining assays to intact tissues, as evidenced by compatibility with 28 antibodies to both endogenous antigens and transgenic reporters like GFP. When applied to degenerating neurons, iDISCO revealed unexpected variability in number of apoptotic neurons within individual sensory ganglia despite tight control of total number in all ganglia. It also permitted imaging of single degenerating axons in adult brain and the first visualization of cleaved Caspase-3 in degenerating embryonic sensory axons in vivo, even single axons. iDISCO enables facile volume imaging of immunolabeled structures in complex tissues. PAPERCLIP: