Fig. 6

Axo-axonic synaptic connections from utricular afferents to horizontal canal afferents. (A) Sagittal projection of reconstructions of three utricular afferents (yellows) and three horizontal canal afferents (greens). Each utricular afferent makes a synaptic connection onto one canal afferent, shown as small circles in the inset panel. Notably all of these apparent connections were found in the ascending branch of the utricular afferent before its central bifurcation, where no other synaptic connections were identified. Inset letters indicate the two synaptic connections shown in panels B and C. (B) Electron micrograph of one of the axo-axonic synapses shown in (A). The utricular afferent (pseudocolored yellow) appears to have multiple release sites onto the canal afferent (pseudocolored green). Scale bar applies to both B and C. (C) As in (B), for a second connection. The postsynaptic density is less pronounced in this image, but nonetheless the clustered vesicles suggest a synaptic connection.