Fig. 1.

Effects of activation of neurons in the ventrolateral medulla (VLM) on cold-evoked BAT thermogenesis. A: the stimulation of brown adipose tissue (BAT) sympathetic nerve activity (SNA) (to 467% of the control level at 36.8°C) and BAT thermogenesis by a reduced core temperature (to 35.6°C at trace onset) was reversed by nanoinjection of N-methyl-d-aspartate (NMDA) into the right VLM [BAT SNA to 94% of control, BAT temperature (Temp): −1.1°C from 35.5°C], which also lowered expired (Exp) CO₂ and heart rate (HR) and increased mean arterial pressure (MAP). A similar pressor response, elicited by phenylephrine (PE) [intravenous (iv)], reduced HR, but did not change BAT SNA (95% of pre-PE control). Nanoinjection of bicuculline (Bic; 30 pmol) into the right VLM also reversed cooling-stimulated BAT thermogenesis (BAT SNA: to 106% of the control level at 36.8°C; BAT Temp: −3.2°C), as well as Exp CO₂ and HR, while increasing MAP. B: the anatomical distribution and relative effects on cold-evoked BAT SNA of NMDA nanoinjection sites in the VLM. Schematic anatomical drawings adapted from Ref. 45. py, pyramidal tract; RPa, raphé pallidus; VII, facial nucleus; bpm, beats/min.