Abstract
In the rhythmic brainstem slice preparation, spontaneous respiratory activity of pre-Botzinger complex (PBC) is generated endogenously and can be recorded as output activity from hypoglossal XII nerve rootlets. We used reduced medullary slice preparations and analyzed changes of spontaneous respiratory activity to elucidate the mechanisms for respiratory rhythm generation. The transverse medullary slices (700-1500 μm) was prepared from neonatal rats and/or mice (1-5 days old Wistar rats and ICR mice). Rhythmic respiratory bursts were recorded from hypoglossal XII nerve rootlets with glass suction electrodes. During recordings, slices were continuously superfused (3-4 ml/min) with mock cerebrospinal fluid with elevated extracellular K+ concentration (5-10 mM) equilibrated with carbogen (95% O2 and 5% CO2), pH 7.4 at room temperature (~26°C). When rhythmic respiratory bursts (2-7 bursts/min) were observed, transverse slice preparations were cut in half along the mid-line (mid-sagittal transections) and reduced to half slices. In half slice preparations, rhythmic respiratory bursts (1-5 bursts/min) could be recorded. To determine the respiratory bursting frequency generated in hypoglossal nerve rootlets, consecutive respiratory cycles were measured and compared before and after mid-sagittal transections. Similar respiratory bursts with slightly decreased frequency were observed after mid-sagittal transection. These results demonstrate that PBC neurons in one half slice are capable of generating rhythmic respiratory bursts. [Jpn J Physiol 54 Suppl:S110 (2004)]
