Abstract The characteristic signaling and intra-spinal projections of muscle proprioceptors best described in the cat are often generalized across mammalian species. However, species-dependent adaptations within this system seem necessary to accommodate asymmetric scaling of length, velocity, and force information required by the physics of movement. In the present study we report mechanosensory responses and intraspinal destinations of three classes of muscle proprioceptors. Proprioceptors from triceps surae muscles in adult female Wistar rats anesthetized with isoflurane were physiologically classified as muscle spindle group Ia or II or as tendon organ group Ib afferents, studied for their firing responses to passive-muscle stretch, and in some cases, labeled and imaged for axon projections and varicosities in spinal segments. Afferent projections and the laminar distributions of provisional synapses in rats closely resembled those found in cat. Afferent signaling of muscle kinematics was also similar to reports on cat, but rat Ib afferents fired robustly during passive muscle stretch and Ia afferents displayed an exaggerated dynamic response, even after accounting for locomotor scaling. These differences in mechanosensory signaling by muscle proprioceptors may represent adaptations for movement control in different animal species.
from #ORL-AlexandrosSfakianakis via ola Kala on Inoreader http://ift.tt/2uResyN
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