Search

Background: Muscle weakness negatively affects perioral muscles and quality of life. The button‐pull exercise is used to teach lip closure (LC) and to strengthen muscles. However, how the muscles accomplish LC during button‐pull and its training effect on each muscle are unknown. Objectives: This study aimed to investigate the LC mechanism and the efficacy of perioral muscle training. Methods: Electromyographic (EMG) activities were obtained from perioral muscles along with the lip closing force (LCF) and were normalised to the maximum LC activities. Correlations between muscle activities and LCF were assessed during LCF increment/decrement task. The effectiveness of training methods was evaluated during functional face tasks (FFT). The effects of button‐pull on muscles were evaluated during static loadings with two sized buttons. Results: The muscles were active during LC, and the amplitudes changed with the LCF. In FFT, the muscles were simultaneously active and the total activity was highest during the blowing task. In button‐pull, maximum button‐pulling forces (BPFs) were significantly larger with the large button (p =.0001). In the static loading task, muscle activities increased with increasing button load. However, the small button produced significantly greater EMG activity than the large button in most of the load (p <.005). Conclusion: LC is accomplished by the cooperation of perioral muscles. In button‐pull, a larger button requires a larger BPF, but a smaller button shows higher muscle activities. Face expression exercises compare favourably with button‐pull. Forceful LC and blowing tasks may be effective and balanced training of the perioral muscles. [ABSTRACT FROM AUTHOR]

Objective: To test a novel sensor for assessing lip function. Methods: The electromyographic (EMG) activity of the upper orbicularis oris muscle (OOM), lip‐closing pressure (LP) and intraoral baro‐pressure (IP) were simultaneously recorded in 20 healthy subjects (10 women and 10 men) by using a novel composite sensor (CS). Subjects performed the lip‐closure, blow and suck tasks. EMG activity of the upper and lower OOMs was recorded using conventional surface electrodes to evaluate the accuracy of CS electrodes. The subjects also rated the user‐friendliness of the CS. Results: Integrated EMG signals recorded using the CS and conventional electrodes from the upper OOM were highly correlated (r = 0.77 ± 0.12 in women and r = 0.81 ± 0.10 in men). The signal‐to‐noise ratio was higher with the CS than with the conventional electrodes. The mean LP during maximum lip closure, blowing and sucking ranged between 2 and 6 kPa in women and between 5 and 7 kPa in men. The corresponding IPs in women were 0.0 ± 0.5, 3.2 ± 1.4 and −4.4 ± 2.6 kPa, respectively, and in men were −0.5 ± 1.4, 4.9 ± 1.8 and −5.6 ± 2.8 kPa, respectively. All subjects rated the recording technique as excellent or good. Conclusion: The CS was highly user‐friendly and accurate in recording the EMG activity of the OOM and could simultaneously measure the LP and IP. Therefore, it could be an effective tool for evaluating lip function. [ABSTRACT FROM AUTHOR]

Merkel cells (MCs) have been proposed to form a part of the MC-neurite complex with sensory neurons through synaptic contact. However, the detailed mechanisms for intercellular communication between MCs and neurons have yet to be clarified. The present study examined the increases in intracellular free Ca2+ concentration ([Ca2+]i) induced by direct mechanical stimulation of MCs. We also measured [Ca2+]i in the trigeminal ganglion neurons (TGs) following direct mechanical stimulation to the MCs in an MC-TGs coculture. The MCs were isolated from hamster buccal mucosa, while TGs were isolated from neonatal Wistar rats. Both cell populations showed depolarization-induced [Ca2+]i. Direct mechanical stimulation to MCs increased [Ca2+]i, showing stimulation strength dependence. In the MC-TGs coculture, the application of direct mechanical stimulation to MCs resulted in increased [Ca2+]i in the TGs. These changes were significantly suppressed by antagonists of glutamate-permeable anion channels (4,4′-diisothiocyanato-2,2′-stilbenedisulfonic acid; DIDS), and non-competitive antagonist of the N -methyl- D -aspartate (NMDA) receptors (MK801). Apyrase, an ATP-degrading enzyme, and suramin, a non-selective P2 purinergic receptor antagonist, did not exert inhibitory effects on these [Ca2+]i increases in the TGs following MC stimulation. These results indicated that MCs are capable of releasing glutamate, but not ATP, in response to cellular deformation by direct mechanical stimulation. The released glutamate activates the NMDA receptors on TGs. We suggest that MCs act as mechanoelectrical transducers and establish synaptic transmission with neurons, through the MC-neurite complex, to mediate mechanosensory transduction. [ABSTRACT FROM AUTHOR]

The ionotropic P2X receptor, P2X7, is believed to regulate and/or generate nociceptive pain, and pain in several neuropathological diseases. Although there is a known relationship between P2X7 receptor activity and pain sensing, its detailed functional properties in trigeminal ganglion (TG) neurons remains unclear. We examined the electrophysiological and pharmacological characteristics of the P2X7 receptor and its functional coupling with other P2X receptors and pannexin-1 (PANX1) channels in primary cultured rat TG neurons, using whole-cell patch-clamp recordings. Application of ATP and Bz-ATP induced long-lasting biphasic inward currents that were more sensitive to extracellular Bz-ATP than ATP, indicating that the current was carried by P2X7 receptors. While the biphasic current densities of the first and second components were increased by Bz-ATP in a concentration dependent manner; current duration was only affected in the second component. These currents were significantly inhibited by P2X7 receptor antagonists, while only the second component was inhibited by P2X1, 3, and 4 receptor antagonists, PANX1 channel inhibitors, and extracellular ATPase. Taken together, our data suggests that autocrine or paracrine signaling via the P2X7-PANX1-P2X receptor/channel complex may play important roles in several pain sensing pathways via long-lasting neuronal activity driven by extracellular high-concentration ATP following tissue damage in the orofacial area. [ABSTRACT FROM AUTHOR]