INVIVO RELEASE OF CALCITONIN GENE-RELATED PEPTIDE-LIKE MATERIAL FROM THE CERVICOTRIGEMINAL AREA IN THE RAT - EFFECTS OF ELECTRICAL AND NOXIOUS STIMULATIONS OF THE MUZZLE

The continuous perfusion with an artificial cerebrospinal fluid of the cervicotrigeminal area of the spinal cord in halothane-anaesthetized rats allowed the collection of calcitonin gene-related peptide-like material with the same immunological and chromatographic characteristics as authentic rat alpha-calcitonin gene-related peptide. The spinal release of calcitonin gene-related peptide-like material could be significantly increased by the local application of 60 mM K+ (approximately + 100%), high-intensity percutaneous electrical stimulation (approximately + 200%) and noxious heat (by immersion in water at 52-degrees-C; approximately + 150%) applied to the muzzle. By contrast, noxious mechanical (pinches) and chemical (subcutaneous formalin injection) stimulations and deep cooling (by immersion in water at 0-degrees-C) of the muzzle did not alter the spinal release of calcitonin gene-related peptide-like material. In addition, low-intensity electrical stimulation, recruiting only the Aalpha/beta primary afferent fibres, significantly reduced (approximately - 30%) the release of calcitonin gene-related peptide-like material from the cervicotrigeminal area. These data suggest that among the various types of natural noxious stimuli, noxious heat may selectively excite calcitonin gene-related peptide-containing Adelta and C primary afferent fibres projecting within the dorsal horn of the spinal cord, and that activation of Aalpha/beta fibres reduces spontaneous calcitonin gene-related peptide-like material release possibly through an inhibitory presynaptic control of calcitonin gene-related peptide-containing Adelta/C fibres.