Naokazu Asanuma

The Endogenous Opioids Related with Antinociceptive Effects Induced by Electrical Stimulation into the Amygdala

Pain relief is necessary and essential for dental treatments. Recently, the relationships of pain and emotion were studied, and electrical stimulation applied to the amygdala depressed the nociceptive response in the anterior cingulate cortex (ACC). Thus, the antinociceptive effects of the amygdala are elucidated, but its mechanism is not yet clarified. The present study was performed to investigate whether endogenous opioid system is related to the depression, and the quantitative changes of endogenous opioids induced by electrical stimulation to the amygdala. We investigated immunohistologically c-Fos expression to confirm the activated neurons, as well as the distribution and the amount of endogenous opioids (β-endorphin, enkephalin and dynorphin A) in the brain using male Wistar rats, when electrical stimulation was applied to the central nucleus of the amygdala (CeA) or noxious stimulation was delivered to the peripheral tissue. c-Fos expression in the ipsilateral ACC was increased by electrical stimulation to the CeA. However, only a small amount of endogenous opioids was observed in the ACC when noxious stimulation or electrical stimulation was applied. In contrast, the amount of dynorphin A in the periaqueductal gray (PAG) was increased by electrical stimulation to the CeA, and the amount of β-endorphin in the PAG was increased by noxious stimulation to the peripheral tissue. The results suggest that dynorphin A in the PAG induced by electrical stimulation to the CeA activate the descending antinociceptive system, and suggest that the nociceptive response in the ACC is depressed indirectly.

Cytochemical localization of cyclic 3′,5′-nucleotide phosphodiesterase activity in the rat olfactory mucosa

SummaryCyclic 3′,5′-nucleotide phosphodiesterase activity was demonstrated cytochemically in the rat olfactory mucosa using cyclic AMP as substrate. Strong activity was observed on the plasma membrane of the cilia, dendritic knob and axon of olfactory cells; weak activity was apparent on the membrane of the dendritic shaft and cell body. This suggests that the cyclic AMP produced by odorant-sensitive adenylate cyclase in the dendritic terminal acts mainly in its original site and to a lesser extent in the dendritic shaft and cell body. The enzyme also hydrolysed cyclic GMP but the hydrolysis was not as great as in the case of cyclic AMP. Besides its presence in olfactory cells, enzymatic activity was also observed on the plasma membrane of basal cells and certain supporting cells with an astrocyte-like morphology.

Newly designed gustatory test based on the number of chewing strokes required for recognition of the taste

PURPOSE The purpose of this study was to examine the usefulness of a new gustatory test based on the progress of mastication by counting the number of chewing strokes required for recognizing tastes. METHODS Thirty-nine subjects (20 males and 19 females, 25.3±6.4 years old) without missing teeth were selected. Four types of newly designed test materials made from 15% gelatine were prepared, containing sucrose, sodium chloride, tartaric acid, or quinine hydrochloride. Five or six concentrations, representing weak to strong tastes, were prepared for each tastant. Subjects were instructed to chew the food, and the number of chewing strokes necessary to recognize the taste was counted. RESULTS Female subjects recognized the sweet taste more accurately than male subjects (Friedman test: p<0.05). For each tastant of the test materials, the average number of chewing strokes (recognition threshold) was approximately 10. The frequency of correct responses and the average number of chewing strokes tended to be higher and lower, respectively, as the concentration of the taste in the test material increased (Kruskal-Wallis test: sweet p<0.01, salty p<0.01, sour p<0.01 and bitter p<0.01). CONCLUSIONS Using the newly designed test materials, counting the number of chewing strokes necessary for recognizing the taste would be a useful index of a new gustatory test to investigate taste sensation.

Factors Related with the Number of Chewing Strokes for Recognizing Taste

Abstract The sense of taste has been evaluated mostly by investigating the taste perception threshold of taste solutions; however, few studies have examined the spread of taste in terms of the masticatory process. We examined the factors related with the number of chewing strokes for recognizing taste. Forty-three subjects without missing teeth were instructed to chew food samples made from 3% agarose containing 2 or 5% sucrose. The number of chewing strokes needed to recognize sweetness in either a partial area or the whole area of the tongue was counted using electromyography. In addition, masticatory performance, salivary flow rate, maximum bite force and scores of oral health related to quality of life (Oral Health Impact Profile, OHIP) were assessed. Male subjects exhibited a larger number of chewing strokes to recognize taste than female subjects for the 5% sucrose sample. The number of necessary chewing strokes for the taste recognition in the whole area was larger than that in a partial area of the tongue. Moreover, some relationships between the count and experimental conditions were found, such as masticatory performance (Spearmans correlation coefficient by rank test: rs=0.49), salivary flow rate (rs= − 0.53), maximum bite force (rs= − 0.43) and scores of OHIP (rs=0.44 — 0.66). The findings suggest that the number of chewing strokes for recognizing sweetness might be affected by the aesthetic feeling against the teeth and oral conditions.

Distribution and origin of VIP‐, SP‐, and phospholipase Cβ2‐ immunoreactive nerves in the tongue of the bullfrog, Rana catesbeiana

Previous studies have found a few intralingual ganglionic cells that were immunoreactive to vasoactive intestinal polypeptide (VIP) in the frog. A recent study reported a large number of such cells, and the possibility of the release of substance P (SP) from these. The aim of the present study was to investigate the distribution, origin, and colocalization of VIP‐ and SP‐ immunoreactive nerves in the tongue of the bullfrog, R. catesbeiana. In addition, the study also examined the colocalization of SP and phospholipase Cβ2 (PLCβ2) in the tongue and jugular ganglion. VIP immunoreactivity was seen in unipolar cells that were sparse in nerve bundles in the submucosal and muscle layers. The density of VIP‐immunoreactive cells was approximately 4.8 cells/mm3. Their fibers terminated in the vicinity of the epithelial basal layer of the fungiform papillae. SP immunoreactivity was not seen in the VIP‐immunoreactive cells, but was observed in pseudounipolar cells in the jugular ganglion. The SP fibers terminated close to the free surface, showing spindle‐ and button‐like profiles. Transection of glossopharyngeal nerve resulted in the persistence of VIP‐immunoreactive cells and the disappearance of SP‐immunoreactive fibers in the tongue. SP immunoreactivity was co‐expressed with PLCβ2 in both the tongue and jugular ganglia. No PLCβ2 immunoreactivity was seen in cells comprising the epithelial taste disk. These findings indicate that the origin of VIP nerve fibers are unipolar cells in the tongue, and SP and PLCβ2 fibers originate from pseudounipolar cells that may be able to release SP primarily in the jugular ganglion. Anat Rec, 299:929–942, 2016.

Electron Microscopic Demonstration of Guanylate Cyclase Activity in Rabbit Taste Bud Cells

The possible involvement of cyclic nucleotide in sweet taste transduction has been reported [1]. The present study was undertaken to explore the possibility of cyclic GMP involvement in taste transduction by cytochemically localizing guanylate cyclase activity in taste bud cells.