Spindles are doin' it for themselves: Glutamatergic autoexcitation in muscle spindles

Summary: The muscle spindle afferents are slowly adapting low threshold mechanoreceptors responsible for reporting muscle length and movement information important for motor control and proprioception. The rapidly adapting cation channel PIEZO2 is essential for muscle spindle afferent stretch sensitivity, but additional molecular elements are required for mediating the complex slowly adapting response of these afferents. Glutamate released from synaptic-like vesicles plays a crucial role in maintaining muscle spindle afferent excitability during stretch, suggesting a potential therapeutic target for normalizing their function.

Summary: The debate over mechanosensory transduction in proprioceptors and low threshold mechanosensory nerve terminals has been ongoing for decades, with a focus on the role of ion channels in encoding stimulus speed and duration. Recent discoveries suggest that Piezo2 may play a key role in regulating the abundance of axolemmal MST complexes, potentially reconciling conflicting observations in the field.