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The coordination between nasal breathing and non-nutritive swallowing serves as a protective reflex against potentially asphyxiating material, i.e. saliva and secretions, entering the respiratory tract. Although this protective reflex is influenced by positional changes in the head and body, the effect of mandible position on this reflex is not fully understood. We examined the effect of mandible advancement associated with mouth opening on the coordination between nasal breathing and non-nutritive swallowing induced by continuous infusion of distilled water into the pharyngeal cavity. The combination of mandible advancement and mouth opening increased the duration of swallowing apnoea and submental electromyographic burst duration. When the mandible was advanced with the mouth open, the duration of swallowing apnoea increased significantly compared with the centric position (0.79 +/- 0.23 vs. 0.64 +/- 0.12 s, P < 0.05, n = 12), and the duration of submental electromyographic activity increased significantly (2.11 +/- 0.63 vs. 1.46 +/- 0.25 s, P < 0.05, n = 12). Mandible advancement with mouth opening altered the respiratory phase resetting during swallowing and the timing of swallow in relation to respiratory cycle phase. We conclude that mandible re-positioning may strongly influence the coordination between nasal breathing and non-nutritive swallowing by altering respiratory parameters and by inhibiting movement of the tongue-jaw complex.

Some intravenous anesthetic agents such as midazolam are known to induce anterograde and retrograde amnesia. We analysed the effect of midazolam by the conditioned taste aversion (CTA) acquisition and retention. After the rats were offered 0.1% sodium saccharin (Sac) as conditioned stimulus (CS), an intraperitoneal (i.p.) injection of several concentrations (5 ~ 30 mg/kg) of midazolam was followed by an i.p. injection of 0.15 M LiCl (2% of body weight) as unconditioned stimulus (US). The rats, which acquired CTA by every CS-US paradigm, strongly avoided Sac on the 1st test day after conditioning and maintained the avoidance for 3 days. We have already reported that Sac intake abruptly increased on the 2nd test day and the almost complete extinction occurred on the 3rd test day after conditioning by injection of subhypnotic dose of propofol before LiCl-injection. In contrast, we found that subhypnotic dose of midazolam suppressed not only CTA acquisition, but also CTA retention. On the other hand, an α2-adrenergic blocker, yohimbin (1 mg/kg) suppressed only the CTA retention. These results suggest that the subhypnotic doses of midazolam firstly affect the acquisition mechanism of the CTA memory (CTAM ), resulting the suppression of the retention of CTAM.Key words: midazolam ; CTA; memory; acquisition; extinction; amnesia, Yohimbin, noradrenergic system -3 -Intravenous anesthetics such as midazolam, one of benzodiazepine anesthetic agents, which possess both γ-aminobutylic acid (GABA)-like [13,29], are known to induce anterograde and retrograde amnesia in human [16,17] and rodents [24,26]. In rodents, it has been reported that anterograde amnesia of an avoidance task was elicited by subhypnotic doses of the intravenous anesthetics, but retrograde amnesia was induced merely by hypnotic doses of these anesthetics [24,25,27].Previous works using a CTA paradigm, where conditioned taste aversion memory (CTAM) related to malaise is formed when an animal consumes a novel taste such as saccharin (conditioned stimulus, CS) and then experiences the symptoms of poisoning such as LiCl (unconditioned stimulus, US) [9], show that the strong CTA is established rapidly by novel taste stimuli in a single learning procedure [5,32]. The association between the CS and the US can proceed under deep anesthesia induced by pentobarbital or ketamine when hypnotic doses of these anesthetics are administrated after CS-presentation, or subhypnotic doses of them, which do not impair drinking, was applied before CS-presentation [6,33].However, subhypnotic doses of the intravenous anesthetics are often used for disabled patients even in light operation such as extraction of teeth to sedate their hyperactivity [22,31]. We often encounter patients, who have lost the memory during operation after administration of sedative dose of these intravenous anesthetics while they preserved their consciousness during operation [22]. In the previous paper [15], we reported that subhypnotic but not hypnotic doses of propofol, one of non-benzodiazepine...

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Chief: Prof. Imao Sunada)The purpose of this study was to observe the pathological changes in the exposed pulp in the germ-free Wistar rats compared with those in the conventional rats.Pulp tissues of the rats were exposed with No. 19 carborundum point or No. 1/2 round bur and the exposures were left unsealed.In order to study the growth of the newly produced calcified tissues, the rats were injected intraperitoneally every 5 days with an aqueous solution of lead disodium ethylene diamine tetraacetate.The animals were sacrificed at 14 and 28 days after the pulp exposure.The results obtained were as follows: 1. In the pulp tissues of the conventional rats, a high percentage of extensive necrosis and inflammatory cell infiltration was observed and even periapical abscess was recognized frequently. Dentine bridge formation was not seen.2. In the pulp tissues of the germ-free rats, although odontoblast disturbance, proliferation of fibroblasts and slight infiltration of the inflammatory cells were observed, dentine bridge formation occurred in 30 per cent of the teeth in 14 days and 57 per cent in 28 days after the pulp exposure.The lead lines by the time-marking method, however, were not clearly seen in the dentine bridge.3. Pulp tissues exposed with a round bur were more damaged than those exposed with a carborundum point in both the conventional and germ-free rats.4. There was no apparent difference between the histologic changes of the injured pulp tissues in the 8 to 11-week-old germ-free rats and those in the 29-week-old rats.

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