Identification of a juxtapara (JXP)-axon initial segment (AIS). Triple immunostaining of ankyrin G (AnkG) (A, E), contactin-associated protein (Caspr) (B, F) and voltage-gated potassium (Kv)1 channels (C, G) (Caspr and Kv1 are merged in (D, H)) along the axon of motor neurons (MNs) labeled with the anti-Peripherin antibody (data not shown). The Caspr+ segment is immediately followed by a Kv1+ segment: Kv1.1+ (D) and Kv1.2+ (H). Triple immunostaining of AnkG (I), Kvβ2 (J) and Kv1.1 (K) (Kvβ2 and Kv1.1 are merged in (L) along the axon of MNs. Brackets indicate the Kv1+ or Kvβ2+ AIS and JXP-AIS and the Caspr+ para-AIS. Scale bar = 5 μm.