Intra-ventromedial hypothalamic injection of glutamate stimulates brown adipose tissue thermogenesis in the rat

Abstract

The ventromedial hypothalamic nucleus (VMH) has been recognized for its role in the control of thermogenesis in brown adipose tissue (BAT) in the rat. However, the neural elements within the VMH that might be involved have not been clearly identified. In the present study, intra-VMH microinjections of the excitatory amino acid glutamate (100 mM to 1 M, in 0.25 microliters), which excites cell bodies and dendrites but not axons and nerve terminals, dose-dependently increased interscapular BAT (IBAT) temperature in urethane-anaesthetized rats. This effect of glutamate was blocked by prior treatment with the sympathetic ganglionic blocker, chlorisondamine chloride (2.5 mg/kg, i.p.) or the beta-adrenergic receptor antagonist, propranolol (2.5 mg/kg, i.p.), implicating the involvement of sympathetic norepinephrine. These results are consistent with the view that cells in the VMH are implicated in the transmission of thermogenic signals to BAT.