The size distribution of neuronal cell bodies, which may approximately reflect the diameters of axons, seems to be in accordance with the above distribution

in that the ratio of small cells (below 20 μm) labeled by in vivo tracing from the periosteum in our previous examination is lower than the ratio of small neurons labeled by ex vivo tracing of the spinosus nerve – compare figure 2d of Schueler et al[24] with Figure 3D of the present paper. Whereas the role for Aβ-fibers in meningeal nociception is unclear, there is good reason to assume that the skull penetrating, presumably nociceptive, Aδ and C-fibers are involved in the generation of headaches. This pattern of innervation could, for example, explain the aggravating influences of neck muscle click here tension on tension-type headache and migraine,[38, 39] and may explain why manual therapies of pericranial structures can be successful in the management of

headaches.[40] It may also partly be an explanation for the beneficial effects of local anesthetic or botulinum toxin injections into peripheral nerves, or the so-called trigger points of pericranial tissues.[41, 42] The dominance of small labeled cell bodies in GPCR Compound Library manufacturer the trigeminal ganglion is in accordance with the dominant number of unmyelinated axons counted in the electron micrographs of the cross-sected spinosus nerve. The cell bodies of the retrogradely labeled trigeminal fibers of the spinosus nerve were found exclusively within the maxillary and mandibular divisions of the trigeminal ganglion, ie, more than 70% of neurons were located in the posterolateral part of the mandibular division. This surprising Glutathione peroxidase result is in accordance with our recent study[24] but is not consistent with previous in vivo studies that show an ophthalmic contribution.[36, 43] The most likely reason for this discrepancy between the present and the above studies is the application site of the tracer to the dural tissue around the MMA and near the superior

sagittal sinus, areas that seem to be innervated by neurons both from the mandibular and the ophthalmic division. Strassman et al (2004),[12] using DiI application in formalin-fixed tissue, described two separate systems of nerve fibers in the dura mater, one that runs parallel to the MMA and another with a preferentially orthogonal orientation running from the transverse sinus across the MMA. The latter may arise from tentorial nerve fibers, which origin in the ophthalmic division of the ganglion. In contrast, the present postmortem anterograde tracings enabled the selective application of the tracer to the spinosus nerve, exclusively innervating the dura mater of the middle cranial fossa.