2006 Volume 10 Issue 3 Pages 257-267
【Purpose】The feeding function in mammals changes from suckling behavior to more complex feeding and swallowing functions including mastication. It is noted that the development of and maturation in the central nervous system is essential during this period, therefore, it is necessary to form neuronal circuits involved with feeding and swallowing functions within a specified period of postnatal time. The purpose of this study was to reveal the changes in activation of central neuronal nucleus involved with feeding caused by the weaning condition when the pups begin to shift from suckling to mastication with the observation using the Fos protein（Fos）as a marker of immunohistochemistry.
【Methods】Twenty-seven Sprague-Dawley rats were separated into the following 3 groups (9 pups in each group) at 15 postnatal days：①Early weaning group (feeding on solid food exclusively), ②Unweaned group (sucking milk artificially without feeding on solid food), ③Control group (nursed with dam). Then, at 19 and 21 postnatal days (P19 and P21, respectively) they were perfused for fixation and the brainstem tissues were extracted and prepared by coronal section (50 μm in thickness). The authors counted the number of Fos-immunoreactive (FI) neuronal cells in the nucleus nervi hypoglossi (XII), nucleus tractus solitarius (NTS), and trigeminal nucleus interpolaris (Sp5i) in thebrainstem.
【Resuts】FI cells were obselved in the early weaning group, especially in P19 rats, there were significant differences between these rats and other groups in the number of FI cells in XII and NTS. Otherwise, in P21 rats, a comparison showed no significant differences in the NTS region. In the Sp5i area, observation indicated the greatest number of FI cells in the early weaning pups, and the control group showed the smallest number of FI cens. Consequently, it was thought that differences in feeding or sucking behavior during the weaning stage influence the nervous activity in the central neuronal nucleus associated with feeding and swallowing functions.
【Conclusion】This study suggested that alterations in the neuroactivity in the central neuronal nucleus were related to changes in the food that rat pups feed on during the weaming period.
