2026/03/09 by Antonia Beiersdorfer, Kristina Losse, Jennifer Bostel +7 · 1 voice
Neuroscience · #Olfactory and Sensory Function Studies #Neural dynamics and brain function #Neuroscience and Neuropharmacology Research
paper · pdf · doi:10.64898/2026.03.08.710364
Abstract Cortical projections to cortical and subcortical targets provide top-down modulation that shapes neuronal performance, including gain control and excitation–inhibition balance. However, the contribution of astrocytes to this process remains poorly understood. In the olfactory bulb, the first relay station of odor information processing, bottom-up input is transmitted from olfactory sensory neurons to mitral/tufted (M/T) cells, which project to the olfactory cortex. Context- and state-dependent top-down modulation arises from feedback projections originating in the anterior piriform cortex (aPC) that target granule cells (GCs). We examined how astrocytes respond to bottom-up and top-down neuronal activity using confocal Ca²⁺ imaging, cell-type-specific optogenetics, electrical stimulation, and single-cell electrophysiology. We found that Ca²⁺ signals in astrocytes are selectively triggered by action potential-dependent ATP release from GCs while M/T cells failed to elicit significant astrocytic responses. Although synaptic input from M/T cells depolarized GCs, it was insufficient to induce action potential firing and subsequent astrocyte activation. By contrast, glutamatergic top-down input from the aPC evoked sustained GC firing, leading to ATP-dependent Ca²⁺ signaling in astrocytes. Our results reveal an unappreciated level of complexity in neuron–astrocyte communication, highlighting its cell-type specificity as well as its context- and state-dependence.