Wouterlood F G, Barbas-Henry H A, Lohman A H
Department of Anatomy, Vrije Universiteit, Amsterdam, The Netherlands.
Brain Res. 1988 Oct 25;463(1):198-203. doi: 10.1016/0006-8993(88)90547-1.
Motoneurons in the principal abducens nucleus of the monitor lizard Varanus exanthematicus were identified by retrograde labeling following application of horseradish peroxidase to the abducens nerve. The ultrastructure and synaptology of thirty labeled neurons were studied. We observed a type of axon terminal which forms mixed junctions with the cell bodies and the initial axon segments of labeled motoneurons. The juxtaposed membranes of the terminals and the motoneurons display gap junctions and small asymmetric synaptic specializations. The mixed-junction terminals contain spherical synaptic vesicles which are located immediately adjacent to the synaptic junction. They may originate from local circuit neurons or from neurons extrinsic to the principal abducens nucleus.
