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The role of neurons in the direction-selective retinal circuit in visual processing in the retina and in the visual thalamus

The lateral geniculate nucleus (LGN) of the thalamus is a major retinal target, involved in processing and relaying visual information, including direction selectivity (DS) and orientation selectivity (OS). How DS and OS are organized in the LGN is poorly understood, as well as whether this information is directly inherited from the retina or generated de novo within the LGN. Using extracellular recordings from across the mouse LGN, we studied DS and OS responses and their topographic organization. We found that DS responses are absent in the central visual field, and that their preferred directions are topographically aligned to match translational optic flow patterns in the remaining visual field. OS responses were uniformly distributed throughout the visual field. By eliminating retinal DS in transgenic mice, we found that DS- but not OS-responses in the LGN were dependent on retinal DS. Thus, LGN DS is inherited from the retina, but retinogeniculate transfer may be topography-dependent, optimizing representations that support visually-guided behaviors.

Pain is a self-preservation mechanism, providing warning indicators associated with tissue damage. These indicators are perceived by nociceptive peripheral innervations with the ability to signal the brain. Nociceptive innervations are also a part of the infrastructure of various organs, yet the imprint their activity has on tissue physiology remains understudied. Here, we applied chemogenetics in mice to locally activate cutaneous TRPV1 innervations in naïve skin and found it triggered accelerated anagen onset. This was preceded by a rapid apoptosis of dermal macrophages mediated by neuropeptide calcitonin gene-related peptide (CGRP), followed by an induction of Osteopontin (Spp1)-expressing dermal fibroblasts. Spp1, an extracellular matrix protein and a hair growth promoting factor, was essential for the TRPV1-triggered induction of new regenerative cycling by dormant hair follicles. Specifically, macrophages responsiveness to CGRP was required for the changes in dermal fibroblasts. Finally, we show that epidermal abrasion induced Spp1-expressing dermal fibroblasts and hair growth via a TRPV1 neuron and CGRP dependent mechanism. Collectively, these data demonstrate a role for pain facilitating innervations in coordinating a cellular mechanism that promotes hair growth and the restoration of this important mechano- and thermo-protective barrier