Abstract
The area around the parabrachial nucleus (PB) including the Kolliker-Fuse (KF) nucles is deeply involved in respiratory control, but not enough information is available about the respiratory neurons of this area. In Nembutal-anesthetized, paralyzed, and artificially ventilated rats with intact vagal nerves, we recorded from more than 300 respiratory neurons in the PB and KF areas. The respiratory neurons were densely distributed in the KF nucleus and sparsely in the medial parabrachial nucleus (PBM) and its vicinity. Only few neurons were purely inspiratory (I) and most "inspiratory" neurons had more or less expiratory (E) activity, exhibiting the property of E-I phase-spanning neurons. By far the less number of I-E phase-spanning neurons were recorded, and their firing was labile and weak. The E neurons exhibited augmenting, decrementing or whole-phase expiratory firing patterns. Activity of the respiratory neurons was variously modulated by lung volume, but we could not find non-respiratory neurons whose activity was modulated thoroughly by lung volume. The majority of the respiratory neurons examined by antidromic stimulation had medullary axons, some having axons descending the midline medulla toward the spinal cord. Many E and "inspiratory" neurons projected to the nucleus tractus solitarii (NTS). Some "inspiratory" neurons projected to the hypoglossal nucleus. It was suggested that PB and KF neurons project to motor output nuclei, such as the nucleus ambiguus and the hypoglossal nucleus, as well as to the rhythm-related structures, such as the Botzinger complex and the NTS. [J Physiol Sci. 2006;56 Suppl:S136]
