RESUMEN
Touch perception begins with activation of low-threshold mechanoreceptors (LTMRs) in the periphery. LTMR terminals exhibit tremendous morphological heterogeneity that specifies their mechanical receptivity. In a survey of mammalian skin, we found a preponderance of neurofilament-heavy-chain(+) circumferential endings associated with hair follicles, prompting us to develop a genetic strategy to interrogate these neurons. Targeted in vivo recordings revealed them to be Aß field-LTMRs, identified 50 years ago but largely elusive thereafter. Remarkably, while Aß field-LTMRs are highly sensitive to gentle stroking of the skin, they are unresponsive to hair deflection, and they encode skin indentation in the noxious range across large, spotty receptive fields. Individual Aß field-LTMRs form up to 180 circumferential endings, making them the most anatomically expansive LTMR identified to date. Thus, Aß field-LTMRs are a major mammalian LTMR subtype that forms circumferential endings in hairy skin, and their sensitivity to gentle skin stroking arises through integration across many low-sensitivity circumferential endings.
Asunto(s)
Mecanorreceptores/metabolismo , Tacto , Animales , Axones/metabolismo , Tronco Encefálico/metabolismo , Fenómenos Electrofisiológicos , Folículo Piloso/metabolismo , Filamentos Intermedios/metabolismo , Ratones , Células Receptoras Sensoriales/metabolismo , Piel/citología , Piel/metabolismo , Asta Dorsal de la Médula Espinal/metabolismoRESUMEN
Meissner corpuscles are mechanosensory end organs that densely occupy mammalian glabrous skin. We generated mice that selectively lacked Meissner corpuscles and found them to be deficient in both perceiving the gentlest detectable forces acting on glabrous skin and fine sensorimotor control. We found that Meissner corpuscles are innervated by two mechanoreceptor subtypes that exhibit distinct responses to tactile stimuli. The anatomical receptive fields of these two mechanoreceptor subtypes homotypically tile glabrous skin in a manner that is offset with respect to one another. Electron microscopic analysis of the two Meissner afferents within the corpuscle supports a model in which the extent of lamellar cell wrappings of mechanoreceptor endings determines their force sensitivity thresholds and kinetic properties.