Presence and location of adrenergic nerve endings in the dental pulps of mouse molars

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Abstract
In all, 30 adult (45-day-old) Swiss Webster mice were used for light and electron microscopic examination of the presence, number, and location of adrenergic endings in the first molar teeth. Prior to sacrifice, 10 animals received i.p. injections at 8, 6, 4, and 2 hours of 0.5 cc of 20 mg/kg solution of 5-hydroxydopamine (5-OH-DA) as a label for adrenergic endings. The animals were then anesthetized, perfused with Karnovsky's fixative, and the teeth were postfixed in Osmic acid, decalcified, embedded in methacrylate, and serial-sectioned. The sections were surveyed by light microscopy, and the number and location of nerve endings containing the reduced 5-OH-DA were recorded. Ten control mice were injected with the vehicle solution and prepared in the same manner. A third series of mice were given a single injection of 5-OH-DA, sacrificed, and prepared for ultrastructural study. The molar pulps were divided into four areas to facilitate examination: pulp horns, coronal pulp, bifurcation area, and root pulp. These four areas were further divided into three zones: odontogenic, vascular-related, and nonvascular-associated. The location and number of endings were evaluated, and an average of approximately 70 endings containing the 5-OH-DA were found in each tooth using light microscopy. These represented 35.5 ± 5.2 in the pulp horns; 26.1 ± 2.4 in the central coronal; 5.4 ± 0.7 in the bifurcation, and 5.6 ± 0.9 in the root pulp per tooth. Vascular related endings were found in greatest number, the odontogenic zone next, and free endings least. Verification of location of 5-OH-DA by ultrastructural analysis revealed the false transmitter in vesiculated endings in the four areas and zones of the pulp.