Establishment of a study model for the recovery of oral functions in patients suffering from somatosensory disfunction

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The present study was carried out to establish a study model for the recovery of oral functions in patients suffering from somatosensory disfunction.We used dissociated cell culture of rat suprachiasmatic nucleus (SCN) neurons because the function of the SCN as a circadian pacemaker has been investigated enthusiastically in both in vivo and in vitro. By using a multi-electrode dish, we measured circadian firing rhythms in individual SCN neurons for more than 2 weeks continuously. Cross-correlation analysis of spontaneous action potentials revealed that a neuron pair was functionally connected by synapses when their circadian rhythms were synchronized. No correlation was found between the paired neurons whose circadian rhythms were not synchronized. Desynchronization of the firing rhythms and the disappearance of the cross-correlation after a chronic blockade of neural communication by tetrodotoxin demonstrate a causal relationship between synaptic transmission and rhythm synchrony.Feeding-associated activation of neurons in the medulla oblongata was examined in both developing and adult rats, using the c-fos gene-encoded protein (Fos) as a marker. Neonates were isolated from mothers for 12h on postnatal day 3,7 and 14, and either breast-fed intensively or further isolated for another 3h, and sacrificed. Adult rats were fasted for 24 hours and either given food and water before sacrifice or sacrificed without food intake. In the breast-fed pups, Fos-immunoreactive (FI) neurons were predominantly localized in the nucleus of the solitary tract (NST) and dorsal medullary reticular formation (dRF). Satiated adult rats with food showed similar patterns of Fos expression in both NST and dRF.In contrast, much fewer FI cells were observed in the NST and dRF in the fasted pups and adults. The distinct localization of Fos in fed pups and adults indicates functional significance of the NST and dRF in the feeding behavior.