Because substance p (SP) has been reported to be released from cutaneous sensory nerve endings after hapten application, we determined whether SP participates in contact hypersensitivity (CH) induction by using a SP agonist, GR73632 or δ-Aminovaleryl [Pro 9 , N-Me-Leu 10 ]-substance P 7-11 and a SP antagonist, spantide I. When injected intradermally, SP agonist enhanced CH induced by conventional, but not optimal, sensitizing doses of hapten. By contrast, SP antagonist inhibited the induction

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... CH by optimal sensitizing doses of hapten. Moreover, SP agonist promoted CH induction and prevented tolerance when hapten was painted on skin exposed to acute, low-dose ultraviolet-B radiation. Intradermally