Fig. 9.

Oligodendrocyte-to-astrocyte gap junctions in myelin from suprachiasmatic nucleus after labeling for Cx43 (A) and in oligodendrocyte plasma membrane from supraoptic nucleus after double labeling for Cx43 and Cx30 (B). A, Small gap junction on outer myelin plasma membrane E-face labeled for Cx43 by four 20 nm gold beads (enlarged in adjacent inset). Continuity of the E-face (arrow labeled E) may be traced from the outer layer of myelin (My) to the gap junction. Outer myelin membrane had IMP-free areas and reciprocal patches. Tight junction strands (white arrows) linked a small patch of the second layer of myelin to the outer layer of myelin.B, Four gap junctions (1–4) in somatic plasma membrane of an oligodendrocyte after double labeling for Cx43 (20 nm gold beads) and Cx30 (10 nm gold beads). Two small gap junctions (2, 3) were not labeled, and one (4) was labeled by only two 10 nm gold beads (Cx30). Oligodendrocyte myelin E-faces are almost devoid of IMPs.