Differential Control of Inhibitory and Excitatory Nerve Terminal Function by Mitochondria

Inhibitory neurons shape the brains computational landscape and rely on different cellular architectures and intrinsic properties than excitatory neurons. Maintenance of the overall balance of excitatory (E) versus inhibitory (I) drive is essential, as disruptions can lead to neuropathological conditions, including autism and epilepsy. Metabolic perturbations are a common driver of E/I imbalance but differential sensitivity of these two neuron types to metabolic lesions is not well understood. Here, we characterized differences in presynaptic bioenergetic regulation between excitatory and inhibitory nerve terminals using genetically encoded indicators expressed in primary dissociated neuronal cultures. Our experiments showed that inhibitory nerve terminals sustain higher ATP levels than excitatory nerve terminals arising from increased mitochondrial metabolism. Additionally, mitochondria in inhibitory neurons play a greater role in buffering presynaptic Ca2+ and inhibitory mitochondrial Ca2+ handling is differentially regulated by TMEM65-mediated acceleration of mitochondrial Ca2+ extrusion following bursts of activity. These experiments thus identify differential reliance on mitochondrial function across two major neuron types.