Atypical protein kinase C expression in phrenic motor neurons of the rat

Atypical protein kinase C (PKC) isoforms play important roles in many neural processes, including synaptic plasticity and neurodegenerative diseases. Although atypical PKCs are expressed throughout the brain, there are no reports concerning their expression in central neural regions associated with respiratory motor control. Therefore, we explored the neuroanatomical distribution of atypical PKCs in identified phrenic motor neurons, a motor pool that plays a key role in breathing. Diaphragm injections of cholera toxin B were used to retrogradely label and identify phrenic motor neurons; immunohistochemistry was used to localize atypical PKCs in and near labeled motor neurons (i.e. the phrenic motor nucleus). Atypical PKC expression in the phrenic motor nucleus appears specific to neurons; aPKC expression could not be detected in adjacent astrocytes or microglia. Strong atypical PKC labeling was observed within cholera toxin B labeled phrenic motor neurons. Documenting the expression of atypical PKCs in phrenic motor neurons provides a framework within which to assess their role in respiratory motor control, including novel forms of respiratory plasticity known to occur in this region.