Inhibition of brown adipose tissue thermogenesis by neurons in the ventrolateral medulla and in the nucleus tractus solitarius.

Am J Physiol Regul Integr Comp Physiol. 2010 Jul;299(1):R277-90. Cao WH, Madden CJ, Morrison SF “Neurons in the ventrolateral medulla (VLM) and in the nucleus tractus solitarius (NTS) play important roles in the regulation of cardiovascular and other autonomic functions”. In this study, the authors demonstrated how activation of neurons in the VLM and intermediate NTS affected brown adipose tissue (BAT) thermogenesis. The authors performed a series of microinjection experiment in chloralose/urethane-anesthetized rats to test their hypothesis. First they tested the effects of activation of neurons in the VLM on cold evoked BAT thermogenesis. NMDA (glutamate agonist) was injected in the VLM to observe that it reversed the cold-evoked increase in BAT SNA, thermogenesis and end-expired CO2. Second they tested the effects of disinhibition of neurons in the VLM or in the NTS on BAT thermogenesis under different conditions using bicuculline (GABA-A receptor antagonist), which reversed the increase in BAT SNA, thermogenesis and end-expired CO2. Finally the tested the effects of inhibition of neurons in the VLM and NTS using muscimol (GABA-A receptor agonist), which produced increases in BAT SNA, thermogenesis and end-expired CO2. These effects were reversed using injection of glycine in the rRPa. These findings suggest that BAT thermogenesis is inhibited by activation of VLM and NTS neurons. -Madhan