Neuronal communication imposes a heavy metabolic burden in maintaining ionic gradients essential for action potential firing and synaptic signalling (1). Given its high energy requirements and limited energy reserves, the evolving brain has developed metabolically-efficient wiring (2) and signalling strategies (3, 4) to transmit information. How energy consumption is distributed among different cell types has yet to be established. In this presentation, I will discuss recent work highlighting the bioenergetics of inhibitory GABAergic synapses (5) and the signalling role of reactive oxygen species (mROS) derived from the mitochondria (6). Emerging data suggest that mROS may act as a homeostatic signalling molecule coupling cellular metabolism to the strength of inhibitory transmission.