Linear arrays of homogenous mast cells in the dura mater of the rat

Abstract

Using fluorescence histochemistry, 5-HT, histamine and heparin were colocalized in a large population of cells in the dura mater thereby identifying them as mast cells. In addition, because these cells were highly sensitive to compound 48/80 and were densely packed with granules of a consistent density, they were identified specifically as 'connective tissue' mast cells. Other types of mast cells, i.e. 'mucosal' or 'neurolipomastocytes', were not present in the rat dura mater. 5-HT immunohistochemistry was the best technique for demonstrating that there were populations of mast cells, one associated with each of the two layers of dura. Although shaped differently the type of mast cell in each layer was the same. It was observed that mast cell shape is dependent on the contiguity, density and orientation of its surrounding elements, not its type. In general, mast cells in the outer layer were aligned parallel to the middle meningeal artery and those in the inner layer were parallel to trigeminal nerve branches that coursed obliquely across the middle meningeal artery. Examination of cross-sections of dura revealed that most mast cells also were aligned at the interface between the two dural layers. The linear orientation of mast cells in two planes of each layer suggests a programmed lamellar seeding of these cells during development of the dura. This study also demonstrated that the majority of dural mast cells were more closely related to other connective tissue elements than to blood vessels and nerves. These results (1) are compatible with the suggestion that dural mast cells play a non-obligatory role in the neuroinflammatory response, (2) leave open to question the role of the dural mast cell in headache or the regulation of blood flow, and (3) support evidence that dural mast cells play an important role in connective tissue related functions, e.g. development, inflammatory response to injury and wound repair.

Axon diameters and intradural trajectories of the dural innervation in the rat

“…In the supratentorial dura, rostral to the transverse sinus, mast cells were arranged in the distinctive "linear arrays" (Fig. 2) that have been described previously in this region of the dura (Dimlich et al, 1991). However, the region caudal to the transverse sinus exhibited an entirely different distribution, which included most prominently a dense accumulation in the area immediately caudal to the sinus and medial to the superior cerebellar veins, on either side of the midline (Fig.…”

“…The orientation of the two fibers systems illustrated with the DiI staining was described previously by Dimlich et al (1991). They observed that the connective tissue of the inner and outer dural layers were obliquely oriented relative to each other, and that the nerve fibers and mast cells within each layer were aligned with the connective tissue.…”

“…Dural mast cells have been suggested to contribute to sensory neuron activation and headache (Rozniecki et al, 1999) and their distribution has been described previously, but only for regions rostral to the transverse sinus (Dimlich et al, 1991). Mast cells were identified by their characteristic granules when stained with Toluidine blue.…”

Sensitization and Activation of Intracranial Meningeal Nociceptors by Mast Cell Mediators

“…Although the dura mater is the intracranial structure most heavily innervated by pain fibers, it is also populated by resident mast cells (MCs) in both humans (Artico and Cavallotti, 2001) and rodents (Dimlich et al, 1991;Rozniecki et al, 1999;. These granulated immunocompetent cells, which reside near blood vessels and in apposition to the meningeal nociceptive fibers (Rozniecki et al, 1999), have the capacity to initiate or amplify inflammatory responses by releasing a host of mediators such as histamine, serotonin, cytokines, and various lipid mediators, including leukotrienes (LTs) and prostaglandins (PGs) (Metcalfe et al, 1997;Mekori and Metcalfe, 2000).…”

Neuropeptide Effects in the Trigeminal System: Pathophysiology and Clinical Relevance in Migraine

“…The morphology and immunophenotype of these cells were compatible with mast cells, which have been found to accompany dural arteries in considerable numbers. 28 In vivo treatment of rat dura with mast cell degranulator compound 48/80 causes loss of immunoreactivity for histamine in mast cells, indicating degranulation. The treatment also caused delayed and prolonged activation of meningeal afferents.…”