C-tactile afferents: Cutaneous mediators of oxytocin release during affiliative tactile interactions?. (August 2017)

• Record Type: Journal Article
• Authors: Walker, Susannah C.; Trotter, Paula D.; Swaney, William T.; Marshall, Andrew; Mcglone, Francis P.
• Is Part Of: Neuropeptides. Volume 64(2017)
• Page Start: 27
• Page End: 38
• Publication Date: 2017-08
• Subjects: Oxytocin -- Social -- Pleasant touch -- Pain -- C-fibre -- C-tactile afferent; Neuropeptides -- Periodicals; Neuropeptides; Neuropeptides -- Périodiques; Neuropeptides; Electronic journals; Periodicals; 572.65
• DOI: 10.1016/j.npep.2017.01.001
• Languages: English
• ISSNs: 0143-4179

Abstract

Abstract: Low intensity, non-noxious, stimulation of cutaneous somatosensory nerves has been shown to trigger oxytocin release and is associated with increased social motivation, plus reduced physiological and behavioural reactivity to stressors. However, to date, little attention has been paid to the specific nature of the mechanosensory nerves which mediate these effects. In recent years, the neuroscientific study of human skin nerves (microneurography studies on single peripheral nerve fibres) has led to the identification and characterisation of a class of touch sensitive nerve fibres named C-tactile afferents. Neither itch nor pain receptive, these unmyelinated, low threshold mechanoreceptors, found only in hairy skin, respond optimally to low force/velocity stroking touch. Notably, the speed of stroking which C-tactile afferents fire most strongly to is also that which people perceive to be most pleasant. The social touch hypothesis posits that this system of nerves has evolved in mammals to signal the rewarding value of physical contact in nurturing and social interactions. In support of this hypothesis, we review the evidence that cutaneous stimulation directly targeted to optimally activate C-tactile afferents reduces physiological arousal, carries a positive affective value and, under healthy conditions, inhibits responses to painful stimuli. These effects mirror those, we also review, which have been reported following endogenous release and exogenous administration of oxytocin. Taken together this suggests C-tactile afferent stimulation may mediate oxytocin release during affiliative tactile interactions. Highlights: C-tactile afferents are unmyelinated low threshold mechanoreceptors. They innervate the hairy skin of mammals. Activation of C-tactile afferents is rewarding, reduces arousal and inhibits pain. These effects match those reported in response to endogenous oxytocin release. C-tactile afferents may mediate oxytocin release during tactile interactions.