Capsaicin desensitization

Preexposure to menthol and capsaicin can desensitize the response to other stimuli, i.e. the thermal response to a warm solution or the irritation upon a second application of capsaicin (26,27). After capsaicin desensitization, the nerves no longer respond to burning or stinging but still give sensations of numbness or warmth. This effect is most noticeable upon further stimulation with capsaicin and less for the irritants, cinnamic aldehyde and NaCl. This sensitization and the fact that these sensations build in intensity on repeat application differentiate them from the "basic tastes", which adapt to the sensation on repeated application. 

Manzini, S., Maggi, C.A., Geppetti, P. et al. (1987). Capsaicin desensitization protects from antigen-induced bronchospasm in conscious guinea-pigs. Eur. J. Pharmacol. 138, 307-308. 

Dray, A., Bettaney, J., and Forster, P., Capsaicin desensitization of peripheral nociceptive fibers does not impact sensitivity to other noxions stimnh, Neuroscl Lett., 99, 50, 1989. 

Geppetti, R, Tramontana, M., DelBianco, E., and Fusco, B.M., Capsaicin-desensitization to the human nasal mucosa selectively reduces pain evoked by citric acid, Br. J. Clin. Pharmacol., 35, 178, 1993. 

A further point concerns the differences between the effects of adult and neonatal capsaicin administration. In some respects adult animals which have been treated neonatally with capsaicin show similar functional impairments as adult animals which have been desensitized to the compound. However, as will be elaborated upon below, there is an important distinction between assault of neonatal and adult animals with high doses of capsaicin. For reasons which will become clear, in the adult animals capsaicin has been referred to in the literature as a sensory neuron blocking agent producing at high doses capsaicin desensitization, whereas in neonatal animals it is a sensory neurotoxin producing sensory neuron lesions. ... 

The unmyelinated axons in the cornea of the adult rat have been subject to electron-microscopic scrutiny after local capsaicin desensitization of the eye. This caused impairment of mitochondrial structure similar to... 

Capsaicin desensitization abolished dye leakage in response to a host of agents thought to act on sensory endings but failed to inhibit the inflammatory response produced by substances such as compound 48/80... 

Further tissue-specific effects were observed in membrane preparations obtained from capsaicin-desensitized rats. The basal adenylate cyclase activity was dramatically increased in the preoptic hypothalamus of these animals but unchanged in the cerebellum or cortex. Moreover, in the cerebellum, normal stimulatory responses were obtained, whereas in the preoptic region not only did capsaicin desensitization cause a failure in the ability of capsaicin to stimulate adenylate cyclase in vitro, but it also produced an inhibition of the augmented basal enzyme activity (Jancso and Wollemann, 1977). Prior exposure of cortical membranes to capsaicin in vitro was also found to increase basal adenylate cyclase activity, and this effect was found to be dependent on calcium ions (Horvath et ai, 1979). 

Hori, T., 1980, The capsaicin-desensitized rat behavioral thermoregulation and thermosensitivity of hypothalamic neurons, in Thermoregulatory Mechanisms and Their Therapeutic Implications, (B. Cox, P. Lomax, A. S. Milton, and F. Schonbaum, eds.), pp. 214-216, Karger, Basel. 

SzolcsAnyi, /., and Barth6, L., 1981, Impaired defense mechanism to peptic ulcer in the capsaicin-desensitized rat, in Advances in Physiological Sciences, Gastrointestinal Defense Mechanisms, (G. Mozik, O. Hanninen, and T./avor, eds.), Vol. 29, pp. 39—51 Pergamon Press, Oxford. 

SzolcsAnyi, /., /o6, F, and /ancs6-GAbor, A., 1971, Mitochondrial changes in preoptic neurons after capsaicin desensitization of the hypothalamic thermodetectors in rats. Nature 229 116-117. 

Silver, W.L., J.R. Mason, J.A. Maruniak D.A. Marshall. 1985. Capsaicin desensitization abolishes aversion to a strong nasal irritant behavioral and electrophysiological evidence that smell and taste remain intact. Brain Res. 333 45-54. 

T Karrer, L Bartoshuk. Effects of capsaicin desensitization on taste in humans. 

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