Background & Aims
Pain sensitivity is thought to be mediated by a combination of biological, psychological and sociocultural factors (Robinson, 2001; Bartley, 2013). It has consistently been shown that women perceive noxious stimuli as more painful than men and are also disproportionally affected by chronic pain conditions (Bartley, 2013; Greenspan, 2007). There has been no study showing sex differences in conduction properties of primary nociceptors. Our aim was to evaluate whether peripheral C-nociceptors show any difference in their conduction properties that might contribute to sex differences in pain perception.
Methods
We retrospectively analyzed microneurography recordings from the superficial peroneal nerve in a group of healthy subjects. The technique was performed as previously described (Serra, 1999). We measured several microneurography parameters, including activity dependent slowing of conduction velocity (ADS) and conduction velocity (CV).
Results
We analyzed a database of 265 healthy volunteers (females 114, age range 19-61 years, median 33? males 151, age range 18-61, median 33) who underwent microneurography over a period of 24 years. A total of 932 C-nociceptors were analyzed (638 mechano-sensitive, 294 mechano-insensitive afferents). We detected statistically significant differences in CV of C-nociceptors between males and females in humans (male 0.77 ± 0.27 m/s, n=469? female 0.60 ± 0.26 m/s, n=378? t-test P<0.001). This difference applied to both mechano-sensitive and insensitive C-nociceptors. Dispersion of conduction velocity was higher for human female C-nociceptors (Coef. Var=43.62%) than for males (Coef. Var=34.96%). Moreover, female C-nociceptors slowed more and recovered slower both at 0.25Hz and at 2Hz. No skin temperature differences were detected to account for this finding.
Conclusions
Our results show a clear sex difference in several basic axonal electrophysiological parameters of C-nociceptors in the largest microneurography database available until now. These differences between male and female C-nociceptors could contribute to the differences in pain sensitivity seen between male and female subjects.
References
•Bartley, E. J. (2013). Sex differences in pain: a brief review of clinical and experimental findings. British Journal of Anaesthesia, 111(1), 52–58.
•Greenspan, J. D.-N. (2007). Studying sex and gender differences in pain and analgesia: a consensus report. Pain, 132 Suppl 1, S26–S45.
•Robinson, M. E. (2001). Gender role expectations of pain: relationship to sex differences in pain. The Journal of Pain, 2(5), 2, 251-257.
•Serra, J. C. (1999). Activity-dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin. The Journal of Physiology 515 ( Pt 3), 799–811.
Presenting Author
Lanhui Qiu
Poster Authors
Ana Benilde Ribeiro
King's College Hospital
Lead Author
Topics
- Gender/Sex Differences