Somatosensory organization and behavior in naked mole‐rats: II. Peripheral structures, innervation, and selective lack of neuropeptides associated with thermoregulation and pain

Abstract

African naked mole-rats are subterranean rodents that have a robust orienting response to stimulation of unique vibrissa-like body hairs that are widely spaced over an otherwise hairless skin. To determine whether these large body hairs have a specialized organization similar to facial vibrissae, the structure and innervation of facial vibrissa follicles, body hair follicles, and intervening skin in naked mole-rats was compared with that in rats and a furred African mole-rat species (the common mole-rat). Immunofluorescence and lectin-binding analyses revealed that the body hair follicles in naked mole-rats were exceptionally large and well innervated, similar to guard hairs of furred species. However, these body vibrissae lacked the anatomic specializations and unique types of innervation affiliated with follicle sinus complexes of facial vibrissae. In contrast to the furred species, naked mole-rats had a paucity of Abeta-fiber Merkel endings at all peripheral locations. Naked mole-rats also were completely lacking in cutaneous C-fibers immunoreactive for substance P and calcitonin gene-related peptide. In contrast, the hairless skin of the naked mole-rats had an exceptional abundance of presumptive Adelta-fibers. The unusual features of the cutaneous innervation in naked mole-rats are presumably adaptations to their subterranean environment and that they are the only known poikilothermic mammal. The features of this mammalian model system provide unique opportunities to discriminate mechanisms related to tactile spatial orientation, vascular regulation, and nociception.

No oxygen? No problem! Intrinsic brain tolerance to hypoxia in vertebrates

“…For example, peripheral insensitivity to chemical irritants (LaVinka et al, 2009), lack of a functional substance P nociceptive pathway (Park et al, 2003), poor thermoregulation (Buffenstein and Yahav, 1991), absence of fur, and high-affinity hemoglobin (Johansen et al, 1976) may all be juvenile characteristics retained into adulthood. Slowed or arrested development might even contribute to the extraordinary lifespan (Buffenstein, 2008) of these remarkable animals.…”

Sensory evolution in blind cavefish is driven by early embryonic events during gastrulation and neurulation

“…Sensory organs also vary greatly among species. Classical cases include the small eyes but highly developed olfactory epithelium of sharks (Collin, 2012), the vibrissae-like tactile hair covering the otherwise hairless skin of the underground-living naked mole rat (Crish et al, 2003;Park et al, 2003;Sarko et al, 2011) or the variation in the number of lateral line neuromasts in sticklebacks depending on their stream versus marine, or benthic versus limnetic, habitat (Wark and Peichel, 2010).…”

Central visual system of the naked mole‐rat (Heterocephalus glaber)

“…Sound attenuates rapidly underground, and presumably because of this environmental constraint, molerats have degraded hearing with poor sound localization abilities (Heffner and Heffner, 1993;Brittan-Powell et al, 2001). However, naked mole-rats are somatosensory specialists with a novel array of somatic vibrissae for guiding orienting behavior (Crish et al, 2003a;Park et al, 2003) and large front incisors used for digging tunnels and manipulating objects. They have a correspondingly hypertrophied somatosensory cortex for processing tactile information that includes a greatly expanded representation of the dentition (Catania and Remple, 2002).…”