Aging reduced mechanical sensitivity of unmyelinated afferents electrically identified in the rat skin-saphenous nerve preparations in vitro

Taguchi, Toru; Ota, Hiroki; Matsuda, Teru; Murase, Shiori; Mizumura, Kazue

doi:10.1016/j.neures.2009.09.1197

Cited by 2 publications

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“…In addition, the ratio of mechano-responsive cutaneous C-fiber afferents has been reported to be lower in aged humans (Namer et al, 2009). We did not use electrical stimulation to search the muscular C-fibers in the present study; however, we have observed a significant decrease of mechanoresponsive cutaneous C-fibers in rats of the same age (130 weeks old, Taguchi et al, 2009). Thus, it is highly possible that the number of afferents which lost mechanical sensitivity also had increased in muscular C-fiber populations.…”

Section: Discussionmentioning

confidence: 73%

“…In our recent experiments, the mechanical response of C‐nociceptors in aged skin tended to decrease (i.e. increased response threshold and decreased magnitude of the mechanical response (Taguchi et al, 2009). In addition, the proportion of cutaneous mechano‐responsive C‐nociceptors significantly decreased in aged S—D rats (Taguchi et al, 2009), as also reported by Namer et al (2009) in middle‐aged human skin (average 56.2 years old) using microneurographic technique.…”

Section: Discussionmentioning

confidence: 94%

“…increased response threshold and decreased magnitude of the mechanical response (Taguchi et al, 2009). In addition, the proportion of cutaneous mechano-responsive C-nociceptors significantly decreased in aged S-D rats (Taguchi et al, 2009), as also reported by Namer et al (2009) in middle-aged human skin (average 56.2 years old) using microneurographic technique. Considering the above, total peripheral C-fiber input to the spinal cord responding to mechanical stimulus to the skin could be attenuated as a function of age.…”

Section: Discussionmentioning

confidence: 99%

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Augmented mechanical response of muscular thin‐fiber receptors in aged rats recorded in vitro

Taguchi

Mizumura

2011

European Journal of Pain

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Musculoskeletal pain deteriorates quality of life by disrupting daily activities and is a considerable economic burden to many countries because of the large number of patients. Little is known about the peripheral neural mechanisms of muscular nociception in the aged, although structural and functional changes in the muscle are apparent as a function of age. The aim of the present study was to investigate the activities of aged muscle nociceptors systematically to mechanical, chemical and thermal stimuli, and to compare with the data from young animals. Activities of single C-fibers were recorded from in vitro preparations of extensor digitorum longus muscle-nerve excised from hind legs of aged rats (125-133 weeks). Mechanical threshold measured by a ramp mechanical stimulus in the aged muscle (median; 45.2 mN (IQR; 38.1-59.1 mN), n=29) was significantly lower than that in the younger muscle (median; 65.4 mN (IQR; 46.6-122.0 mN), n=33, p<0.01, Mann-Whitney U-test) reported in our previous study (Taguchi et al., 2005). In addition, the magnitude of the mechanical response during the first 5s of the 10s stimulus was significantly greater in the aged muscle (11.0 spikes (IQR; 6.5-20.5 spikes)) than in the young (7.0 spikes (IQR; 4.0-11.5 spikes), p<0.05, Mann-Whitney U-test). In contrast, the numbers of discharges induced by chemical (pH 5.5, ATP and bradykinin) and thermal (cold and heat) stimuli were not different with the different ages. These results showed an augmented mechanical response in muscle C-afferents in the aged rats.

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Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

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Augmented mechanical response of muscular thin‐fiber receptors in aged rats recorded in vitro

Taguchi

Mizumura

2011

European Journal of Pain

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Cutaneous C-fiber nociceptor responses and nociceptive behaviors in aged Sprague–Dawley rats

Taguchi

Ota

Matsuda

et al. 2010

Pain

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The change with age in pain perception in humans and the nociceptive behaviors in animals elicited by noxious stimuli to the skin are not well understood, and little is known about the peripheral neural mechanisms of cutaneous nociception in the aged. We systematically examined cutaneous nociceptor responses and nociceptive behaviors in young (9-14 w) and in aged (127-138 w) Sprague-Dawley rats. C-fiber nociceptors in the skin were identified by mechanical and electrical stimulation, and extracellularly recorded from hind paw skin-saphenous nerve preparations in vitro. In the aged rats, the proportions of mechano-responsive and/or heat-responsive C-nociceptors were significantly lower. The proportion of mechano- and thermo-insensitive units, on the other hand, was significantly increased. In addition, the response threshold to mechanical stimulus tended to be higher and the magnitude of the response tended to be smaller. There were no differences between the two age groups in the response magnitudes of mechano-responsive C-nociceptors to bradykinin, cold or heat. Repetitive electrical stimulation of afferent fibers revealed exaggerated slowing of conduction velocity in mechano-responsive C-fibers in the aged. This showed for the first time that not only receptive properties of afferent terminals but also membrane properties of conducting axons are changed in aged rats. Nociceptive behaviors in response to noxious levels of cold (cold plate test) and heat (Hargreaves' radiant heat test) were facilitated in aged animals, while mechanical sensitivity measured by von Frey hairs remained unchanged. These discrepancies between the changes in peripheral afferents and the behavioral outcomes might be explained by facilitatory changes in the central nervous system.

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Aging reduced mechanical sensitivity of unmyelinated afferents electrically identified in the rat skin-saphenous nerve preparations in vitro

Cited by 2 publications

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Augmented mechanical response of muscular thin‐fiber receptors in aged rats recorded in vitro

Augmented mechanical response of muscular thin‐fiber receptors in aged rats recorded in vitro

Cutaneous C-fiber nociceptor responses and nociceptive behaviors in aged Sprague–Dawley rats

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