Fig. 1.

POA-projecting LPBd neurons are activated in a warm environment. Fos expression in LPB neurons that were retrogradely labeled with CTb injected into the MnPO (red, A and E) was examined in rats exposed to control (24 °C) (A–D) or warm (36 °C) (E–H) temperature. Many neurons in the LPBd of the warm-exposed animal exhibited both CTb (brown) and Fos (blue-black) immunoreactivities (arrows, H), whereas most CTb-labeled neurons in the LPBd of the control-exposed animal were negative for Fos immunoreactivity (arrowheads, D). [Scale bars, 0.5 mm (A–C and E–G); 30 μm (D and H).] 3V, third ventricle; ac, anterior commissure; MPO, medial preoptic area; ox, optic chiasm; scp, superior cerebellar peduncle. Some images from the animal exposed to 24 °C were adapted from our previous study (8).