Abstract
We have previously reported a novel functional respiratory neuron group in the limited region of the rostral ventrolateral medulla; 'para-facial respiratory group (pFRG)', ventrolateral to the facial nucleus and close to the ventral surface. Since neuronal activity in the pFRG was demonstrated to precede the inspiratory burst by the optical recordings using voltage sensitive dyes, pre-inspiratory (Pre-I) neurons are a dominant subtype of respiratory neurons in this group. However, we had experience that the electrophysiological recordings of the neurons were rather difficult compared with those in more caudal medulla. The present study was carried out to reveal the more detailed feature of the pFRG in the brainstem-spinal cord preparation from newborn rat. We recorded mainly Pre-I neurons in the pFRG by whole-cell patch clamp and stained them with Lucifer Yellow for subsequent histological analysis. We found that Pre-I neurons were located in the area immediately beneath the ventral pia mater. These neurons had fusiform or spherical cell bodies and the dendrites extending medially and laterally along the ventral surface. The most neurons examined responded with membrane depolarization to substance P or high CO2 (8%) application in the presence of TTX. We concluded that burst activity of such neurons in the superficial ventral region could be a signal source for fluorescence changes detected by the optical recordings, and the characteristic distribution may be a reason for the technical difficulty of whole-cell recordings by the ventral approach. [Jpn J Physiol 54 Suppl:S109 (2004)]
