Stretch Sensitivity of Cutaneous RA Mechanoreceptors in Rat Hairy Skin

Abstract

Robichaud, Daniel R. II, Zaccaria Del Prete, and Peter Grigg. Stretch sensitivity of cutaneous RA mechanoreceptors in rat hairy skin. J Neurophysiol 90: 2065-2068, 2003. First published June 4, 2003 10.1152/jn.00405.2003. Twenty-five rapidly adapting mechanoreceptor afferents were recorded in an in vitro preparation of rat skin and nerve. Single units were recorded while the skin was subjected to dynamic uniaxial stretch using a pseudo-Gaussian noise (PGN) input waveform. Force was the controlled variable in stretch stimuli. Measured loads and displacements were used to calculate tensile stresses, strains, and their rates of change. Associations between spike responses and individual stimulus components such as tensile stress or strain were determined in a reverse correlation design using multiple logistic regression. Spikes were strongly associated with stress, at memory times from 0 to 14 ms, and with the rate of change of stress, at a memory times between 6 and 18 ms. There was a strong interaction between stress and its rate of change, with a maximum value at a memory time of 10 ms. We found no relationship between spike responses and strain. I N T R O D U C T I O NIt is well known that many cutaneous mechanoreceptor afferents can be activated by stretch stimuli (Del Prete et al. 2003;Grigg 1996;Grigg and Hoffman 1996;Kumazawa and Perl 1977; Nordin 1994). However, stretching skin produces a number of mechanical states, such as tensile stress, tensile strain, strain energy density, and their rates of change, in the skin. In general, it has been unclear which of these states might act as the stimulus to the mechanoreceptor ending. Recently, however, several of us (Del Prete et al. 2003) described a method that allows for determining the association between spikes and multiple stimulus variables. This method, which is based on multiple logistic regression (Hosmer and Lemeshow 1989), also allows for determining whether there are memory effects in the association between variables and spikes. "Memory," in this sense, refers to the time between the production of a stimulus in the skin and the appearance of a response in the afferent.The use of logistic regression in applications such as this has been described in detail with reference to mechanoreceptors from mouse skin (Del Prete et al. 2003). In addition, the method was used to re-analyze previously published data from rapidly adapting (RA) afferents in rat skin (Grigg and Del Prete 2002). In both preparations, spikes were strongly associated with the rate of change of tensile stress. However, the two experiments found differences in the memory times at which the effect of that stimulus was observed. Responses in mouse mechanoreceptors were most strongly associated with the rate of change of stress 8 -10 ms before a spike. In contrast, the re-analyzed data from rat skin units showed that the rate of change of stress had its maximal effect on the order of 30 ms prior to a spike. In attempting to account for the differences between these two results, we note that...

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“…The relevant stress and strain quantities utilized were maximum compressive stress, maximum compressive strain, von Mises stress, and strain energy density. Four variables were used because while others have shown that SA-I and RA afferents in the skin encode stress-related quantities better than strainrelated quantities (Khalsa et al 1996(Khalsa et al , 1997Ge and Khalsa 2002;Del Prete et al 2003;Robichaud et al 2003), the issue remains unresolved (Sripati et al 2006). These quantities, in particular, have shown the best correlation with the neural response.…”

Evidence for stress‐dependent mechanoreceptors linking intestinal biomechanics and sensory signal transduction

“…Recent publications also point towards a stress‐dependent mechanism in the skin, i.e. cutaneous rapidly adapting afferent responses were driven by the rate of change of stress (Grigg & del Prete, 2002; Robichaud et al 2003). These phenomena are also consistent with the recent observation of a tension‐dependent mechanism in vagal afferents in the guinea‐pig stomach (Zagorodnyuk et al 2001) and pelvic afferents in the guinea‐pig and mouse rectum (Lynn et al 2003, 2005; Spencer et al 2008).…”