Identification of maxillary factor, a maxillary process-derived chemoattractant for developing trigeminal sensory axons.
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Trigeminal sensory axons project to several epithelial targets, including those of the maxillary and mandibular processes. Previous studies identified a chemoattractant activity, termed Maxillary Factor, secreted by these processes, which can attract developing trigeminal axons in vitro. We report that Maxillary Factor activity is composed of two neurotrophins, neurotrophin-3 (NT-3) and Brain-Derived Neurotrophic Factor (BDNF), which are produced by both target epithelium and pathway mesenchyme and which are therefore more likely to have a trophic effect on the neurons or their axons than to provide directional information, at least at initial stages of trigeminal axon growth. Consistent with this, the initial trajectories of trigeminal sensory axons are largely or completely normal in mice deficient in both BDNF and NT-3, indicating that other cues must be sufficient for the initial stages of trigeminal axon guidance. (+info)
Neurokinetics of lidocaine in the infraorbital nerve of the rat in vivo: Relation to sensory block.
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The kinetics of neural uptake and efflux of lidocaine hydrochloride were studies by means of a standardized technique for blocking the intraorbital nerve of the rat, using a palatal jig. Following injection of 14-C-labeled local anesthetic, groups of ten animals were saccraficed at incipient recovery from sensory block or at othertimes. The nerves were weighed and assayed for radioactivity. The lengths of nerve containing high levels of lidocaine varied inversely with the times elapsed since onset of block. In experiments where a fixed quantity (2 mg) drug was injected, the incidence of block 2 hours later was concentrated-dependent, occuring in 80 per cent of animals after 2 per cent, in 40 per cent after 1 per cent, and in none after 0.5 per cent lidocaine. Epinephrine, 1:200,000, prolonged by 80 per cent the block effected with 0.2 ml of 1 per cent lidocaine. At the onset of recovery the neural contents of lidocaine at the sites of injection were 484 plus or minus 404 ng/mg of nerve in epinephrine-treated nerves, and 274 plus or minus 218 ng/mg in nonepinephrine-treated nerved (N.S., P greater than 0.05). Quantitative comparisons of in-vivo effectiveness of local anesthetic solutions can be made with this technique. (+info)
Tracking the spread of a lacZ-tagged herpes simplex virus type 1 between the eye and the nervous system of the mouse: comparison of primary and recurrent infection.
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The spread of herpes simplex virus type 1 (HSV-1) during primary ocular infection and after reactivation of latent infection in the trigeminal ganglion (TG) was examined in the mouse using a genetically modified virus containing the lacZ reporter gene under the control of the immediate-early 110 promoter. Whole tissue mounts of the eye and lids, their sensory nerves, and TG with the attached dorsal root entry zone (DRE) into the central nervous system (CNS) were stained for beta-galactosidase. Sixteen hours after inoculation of the cornea by scarification, staining was found in the scarified epithelium of the cornea and in the unscarified conjunctiva. By 24 h, staining was also seen in a few TG neurons and by 96 h their number had greatly increased and their distribution was more widespread. Stained cells (identified as Schwann cells by their staining for glial fibrillary acidic protein [GFAP] or S-100) in the TG were first seen close to stained neurons at 40 h, and by 48 h lines of such cells extended partway toward the periphery and toward the DRE. By 72 h, these lines had reached the periphery and the DRE where the adjacent CNS was also stained. In the cornea, stained cells with the morphology and arrangement of Schwann cells were seen from 40 to 120 h. After reactivation of latent infection, 10 of 22 samples had positively stained neurons. In eight samples, corneal and lid epithelial cells were stained. No stained Schwann cells were seen in the TG; however, branched networks of such cells were present in the cornea and the lids. This detailed sequential analysis has provided new information on the involvement of Schwann cells in the pathogenesis of primary and recurrent HSV-1 disease in the TG and the cornea. (+info)
Local anesthesia in the palate: a comparison of techniques and solutions.
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It was the purpose of the present investigation to determine if there were differences in soft-tissue anesthesia in the palate following infiltration and greater palatine nerve block anesthesia and to compare lidocaine with lidocaine plus epinephrine as palatal soft tissue anesthetics. Two studies using 10 volunteers were performed. In one trial, volunteers received a palatal infiltration opposite the second maxillary bicuspid on one side and a greater palatine nerve block on the other. Response to sharp probing and pain-pressure thresholds were measured on each side over a 1-hour census period. In the second trial, volunteers received 2% plain lidocaine as a palatal infiltration on one side and a similar infiltration of 2% lidocaine with 1:80,000 epinephrine on the other in a double-blind randomized fashion. Response to sharp probing was assessed over a 55-minute period. Data were analyzed using Student's paired t tests. The response to sharp probing and pressure-pain thresholds did not differ between palatal infiltration and greater palatine nerve block over the 1-hour period. Lidocaine with epinephrine provided longer lasting anesthesia than plain lidocaine following palatal infiltration (P < .001). Greater palatine nerve block and palatal infiltration provide similar soft-tissue anesthesia. Lidocaine with epinephrine produces longer-lasting soft-tissue anesthesia than plain lidocaine following palatal infiltration. (+info)
Whisker deafferentation and rodent whisking patterns: behavioral evidence for a central pattern generator.
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Even in the absence of explicit stimulation, rats emit patterns of rhythmic whisking movements. Because of their stereotyped nature and their persistence after sensory denervation and cortical ablation, whisking movements have been assumed to reflect the output of a central pattern generator (CPG). However, identification of a movement pattern as the product of a CPG requires evidence that its generation, patterning, and coordination are independent of sensory input. To provide such evidence, we used optoelectronic instrumentation to obtain high-resolution records of the movement trajectories of individual whiskers in rats whose heads were fixed to isolate their exploratory whisking from exafferent inputs. Unconditioned whisking patterns were quantitatively characterized by a biometric analysis of the kinematics, rhythmicity, and coordination of bilaterally homologous vibrissa movements. Unilateral and bilateral sectioning of the infraorbital nerve, which innervates the whiskers, was then performed to block reafferent inputs generated by the animal's own whisking movements. Unilateral sectioning of the nerve has no effect on whisking kinematics but is followed by a significant but relatively transient bilateral increase in whisking frequency. However, bilateral deafferentation, when performed in a single-stage procedure, does not disrupt the generation, patterning, or bilateral coordination of whisking patterns in the rat. These findings provide strong behavioral evidence for a whisking CPG and are discussed in relation to its possible location and properties. (+info)
Effectiveness of 20% benzocaine as a topical anesthetic for intraoral injections.
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The use of topical anesthetics has been advocated prior to the administration of various types of anesthetic injections. Reported results have varied between studies. The purpose of this study was to compare the effectiveness of 20% benzocaine in reducing the pain of needle insertion during maxillary posterior and anterior infiltration and inferior alveolar nerve block injections. In this retrospective study, 1080 patients received 2336 injections using a 27-gauge needle. Topical anesthetic was applied prior to 720 of the injections. Patients rated pain of needle insertion using a 0-4 pain scale. Logistic regression analysis showed no differences in pain ratings between topical and no topical groups for the inferior alveolar nerve block and posterior maxillary infiltration injections. The use of topical anesthetic did reduce the pain of needle insertion with the maxillary anterior injections (P = .0041). (+info)
Optical mapping of the functional organization of the rat trigeminal nucleus: initial expression and spatiotemporal dynamics of sensory information transfer during embryogenesis.
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We examined the functional organization of the rat trigeminal nuclear complex and its developmental dynamics using a multiple-site optical recording technique. Brainstem preparations were dissected from embryonic day 12 (E12)-E16 rat embryos, and stimulation was applied individually to the three branches of the trigeminal nerve (V1-V3). The action potential activity of presynaptic fibers was detected from E13, and the glutamate-mediated postsynaptic response was significantly observed from E15 on. At E14, the evoked signals usually consisted of only the action potential-related fast component. However, when extracellular Mg2+ was removed, a significant dl-2-amino-5-phosphonovaleric acid-sensitive slow component appeared. These results suggest that postsynaptic function mediated by NMDA receptors is latently generated as early as E14. The response area of the three branches of the trigeminal nerve showed some functional somatotopic organization, with the ophthalmic (V1) nerve area medially located and the mandibular (V3) nerve area laterally located. The center of the trigeminal nuclear complex in which the activity of neurons and synaptic function was greatest shifted caudally with development, suggesting that the functional architecture of the trigeminal nuclear complex is not fixed but changes dynamically during embryogenesis. By electron microscopy, we could not observe clear correlations between functional data and morphological information; when we surveyed E16 preparations, we could not identify typical synaptic structures between the 1,1'-dioctyldecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-labeled trigeminal nerve terminals and the neurons in the trigeminal nuclear complex. This implies that postsynaptic function in the trigeminal nuclear complex is generated before the appearance of the morphological structure of conventional synapses. (+info)
Anesthetic efficacy of the anterior middle superior alveolar (AMSA) injection.
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The purpose of this prospective, randomized, blinded study was to determine the anesthetic efficacy of the anterior middle superior alveolar (AMSA) injection using the computer-assisted Wand Plus injection system versus a conventional syringe. The authors, using a crossover design, randomly administered in a blind manner 2 AMSA injections utilizing the computer-assisted injection system and a conventional syringe to 40 subjects during 2 separate appointments. A pulp tester was used to test for anesthesia, in 4-minute cycles for 60 minutes, of the central and lateral incisors, canine, and first and second premolars. Anesthesia was considered successful when 2 consecutive no responses (80 readings) with the pulp tester were obtained. For all teeth, except the central incisor, the use of the computer-assisted injection system was significantly (P < .05) more likely to result in pulpal anesthesia than the use of the conventional syringe technique. For the computer-assisted injection system, successful pulpal anesthesia ranged from 35 to 58%, and for the conventional syringe, successful pulpal anesthesia ranged from 20 to 42%. For both techniques, the onset of pulpal anesthesia was slow, and duration of pulpal anesthesia declined steadily over 60 minutes. We conclude that although the AMSA injection using the computer-assisted injection system was more successful than the conventional syringe technique, the rather modest to low success rates, slow onset, and declining duration of pulpal anesthesia over 60 minutes would not ensure predictable pulpal anesthesia from the second premolar to the central incisor. (+info)