Abstract
The preoptic area of the hypothalamus is a homeostatic control center. The heterogeneous neurons in this nucleus function to regulate the sleep/wake cycle, reproduction, thirst and hydration, as well as thermogenesis and other metabolic responses. Several recent studies have analyzed preoptic neuronal populations and demonstrated neuronal subtype-specific roles in suppression of thermogenesis. These studies showed similar thermogenesis responses to chemogenetic modulation, and similar synaptic tracing patterns for neurons that were responsive to cold, to inflammatory stimuli, and to violet light. A reanalysis of single-cell/nucleus RNA-sequencing datasets of the preoptic nucleus indicate that these studies have converged on a common neuronal population that when activated, are sufficient to suppress thermogenesis. Expanding on a previous name for these neurons (Q neurons, which reflect their ability to promote quiescence and expression of Qrfp), we propose a new name: QPLOT neurons, to reflect numerous molecular markers of this population and to capture its broader roles in metabolic regulation. Here, we summarize previous findings on this population and present a unified description of QPLOT neurons, the excitatory preoptic neuronal population that integrate a variety of thermal, metabolic, hormonal and environmental stimuli in order to regulate metabolism and thermogenesis.
Highlights
Body temperature regulation is key to survival and reproductive fitness with many mechanisms of regulation evolving throughout speciation
Shivering thermogenesis results from rapid muscle contractions, whereas non-shivering thermogenesis takes place in specialized fat depots via uncoupling of mitochondrial gradients from the electron transport chain mediated by uncoupling protein 1 (Ucp1) (Nedergaard et al, 2001)
More work with precise genetic markers will be needed to further understand how these separate neuronal populations may function together to regulate body temperature and arousal
Summary
Body temperature regulation is key to survival and reproductive fitness with many mechanisms of regulation evolving throughout speciation. Activation of QPLOT neurons through various cre lines, either optogenetic or chemogenetic, results in a decrease in body temperature and energy expenditure (Song et al, 2016; Tan et al, 2016; Yu et al, 2016; Hrvatin et al, 2020; Takahashi et al, 2020; Zhang K.X. et al, 2020; Zhang Z. et al, 2020) This effect is likely due to a combination of cutaneous vasodilation, reduced food intake, and a suppression of nonshivering thermogenesis (Abbott and Saper, 2017). More work with precise genetic markers will be needed to further understand how these separate neuronal populations may function together to regulate body temperature and arousal
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