Capsaicin as a tool for studying sensory neuron functions.

The exceptional selectivity with which capsaicin acts on a population of peptide-containing thin primary afferent neurons has made this drug an important tool with which to investigate the neuroanatomical, neurochemical and functional implications of these neurons. As a consequence, the use of capsaicin has enabled a substantial furthering of our understanding of the physiological and pathophysiological roles of thin primary sensory neurons. With appropriate controls, both the acute excitatory and long-term neurotoxic actions of capsaicin can be utilized in these studies but it is important to know the advantages and disadvantages and the limitations of each of the different experimental approaches. Table 1 is a brief checklist of the caveats that should be considered and that have been dealt with in this article.