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. 2022 Mar 29;6:313. Originally published 2021 Nov 17. [Version 2] doi: 10.12688/wellcomeopenres.17379.2

Figure 3. Schematic comparing thermoregulation with torpor induction pathways.

Figure 3.

The current thermoregulatory model (left) proposes predominantly GABAergic projections from POA to DMH. These GABAergic projections are activated by skin, viscera, or CNS warming and pyrogens. DMH contains both glutamatergic and GABAergic neurons, the activation of which causes increased BAT thermogenesis, vasoconstriction, and increased core temperature. The location of the second GABAergic neuron in the relay from DMH to raphe pallidus has not been established. The emerging model for torpor induction (right) suggests glutamatergic / PACAP / QRFP neurons project from POA to DMH. Similar to the effects of activating the GABAergic POA to DMH, activating this excitatory POA to DMH pathway reduces body temperature, and in this case, induces torpor. The nature of the DMH neurons that are activated by the excitatory POA to DMH projection remains unknown. Abbreviations: GABA, gamma-aminobutyric acid; POA, preoptic area; DMH, dorsomedial hypothalamic area; CNS, central nervous system; BAT, brown adipose tissue; PACAP, Pituitary adenylate-cyclase-activating polypeptide; QRFP, pyroglutamylated RFamide peptide (QRFP).