Atypical PKC enzyme activity is elevated in the phrenic motor nucleus 1 and 28 days post-C2 hemisection. Atypical PKC activity was measured in ventral C3–5 homogenates either ipsi- or contralateral to injury from sham (white bar) and C2 hemisection (black bar). (A) After one day of recovery, aPKC activity is significantly increased on the side ipsilateral to injury (C2HS v. sham, p=0.026; ipsi vs. contra, p=0.038) (B) Three days post-injury, there is no significant difference in aPKC activity on either side (p>0.05). (C) 28 days post-injury, aPKC activity is significantly higher in C2 hemisected rats v. shams, regardless of side (p=0.011). In individual comparisions, aPKC activity is increased on the side contralateral to (C2HS v. sham, p=0.018), but not ipsilateral to injury (C2HS v. sham, p=0.096). (D) Atypical PKC activity is significantly increased 28 days versus one day post-injury (p=0.015).