RELEASE OF IMMUNOREACTIVE SUBSTANCE-P IN THE TRIGEMINAL BRAIN-STEM NUCLEAR-COMPLEX EVOKED BY CHEMICAL-STIMULATION OF THE NASAL-MUCOSA AND THE DURA-MATER-ENCEPHALI - A STUDY WITH ANTIBODY MICROPROBES

In order to study a possible involvement of substance P in the process ing of chemonociceptive input from the nasal mucosa and the dura mater encephali in the spinal trigeminal, the release of immunoreactive sub stance P was measured in the trigeminal brain stem nuclear complex in anaesthetized rats. Microprobes coated with antibody to substance P we re inserted into the lateral area of the brain stem up to 1 mm posteri or to the obex corresponding to the trigeminal subnucleus caudalis. Wh en the nasal mucosa was stimulated by topical administration of mustar d oil (1% and 5%) into the nostrils, immunoreactive substance P was ma inly detected in the dorsal region of the trigeminal brain stem nuclea r complex with a maximum in the superficial gray matter. When the dura mater encephali was stimulated by topical administration of Tyrode's solution (pH 6.2), immunoreactive substance P was mainly released in t he ventral region of the trigeminal brain stem nuclear complex; with p H 5.5 the release was more diffuse extending from the ventral to the d orsal part of the spinal trigeminal nucleus. Release was maximal rathe r after than during the administration of the stimuli, and it consider ably outlasted the stimulation periods. These data suggest that substa nce P plays an important role in the processing of chemonociceptive in puts From the nasal mucosa and the dura mater encephali in the trigemi nal brain stem nuclear complex. Substance P may be important, therefor e, in the generation of those headaches that are caused by affections of the nasal mucosa and the dura mater encephali. Since enhanced level s of immunoreactive substance P were present for considerable time per iods beyond the administration of the stimuli, substance P and neuroki nin-l receptors may be involved in long-lasting neuronal events follow ing noxious stimulation. Copyright (C) 1996 IBRO.