Takashi Sasamura and Yasushi Kuraishi (*)
Department of Applied Pharmacology, Faculty of Pharmaceutical Sciences,
Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930
- 0194, Japan
(*) To whom correspondence should be addressed.
Abstract: Vanilloid receptor subtype 1 (VR1), a capsaicin receptor,
is expressed in primary sensory neurons and vagal nerves. Heat and protons
as well as capsaicin activate VR1 to induce the influx of cations, particularly
Ca2+ and Na+ ions. Characteristic effects of capsaicin
are the induction of a burning sensation after acute administration and
the desensitization of sensory neurons after large doses and prolonged administration.
The latter feature made capsaicin cream applicable for the treatment of
chronic pain and pruritus. Capsaicin alters several visceral functions,
which may be mediated by action on vagal nerves and central neurons. Capsaicin
affects thermoregulation after intra-hypothalamic injection and releases
glutamate from the hypothalamus and cerebral cortex slices, while VR1-like
immunoreactivity is not apparent in these regions. These findings taken
together suggest the existence of other subtypes of vanilloid receptors
in the brain.
Keywords: Capsaicin, VR1 receptor, Proton, Heat stimulation, Nociception