AFFERENT-PROJECTIONS TO THE BOTZINGER COMPLEX FROM THE UPPER CERVICALCORD AND OTHER RESPIRATORY-RELATED STRUCTURES IN THE BRAIN-STEM IN CATS - RETROGRADE WGA-HRP TRACING

Following injection of WFA-HRP (30-60 nl, 5%) into the Botzinger compl ex (Botc), a group of expiratory neurons in the vicinity of the retrof acial nucleus, a number of labeled neurons were observed, predominantl y ipsilaterally, in the intermediate zone of the upper cervical cord a t the C-1 and C-2 segments, the retrotrapezoid nucleus (RTN) in the ve ntrolateral medulla and the parabrachial-Kolliker-Fuse nuclear complex in the rostral pens. In addition, clusters of labeled cells were also observed in and around the solitary tract nucleus, nuclei ambiguus an d retroambiguus, and nucleus raphe magnus. Control injections into the magnocellular tegmental field adjacent to the Botc resulted in a diff use distribution of labeled neurons in the reticular formation. These results demonstrate that the Botc receives convergent monosynaptic axo nal projections from the upper cervical spinal cord, the pontine pneum otaxic area, the RTN and several other respiratory related structures in the medulla.