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The fine structure of the lateral vestibular nucleus in the rat. II. synaptic organization

1970; Elsevier BV; Volume: 18; Issue: 1 Linguagem: Inglês

10.1016/0006-8993(70)90459-2

1872-6240

Constantino Sotelo, Sanford L. Palay,

Biochemical Analysis and Sensing Techniques

Three types of axon terminal occur in the lateral vestibular nucleus of the rat: large, slender and small. Large terminals are often seated in cup-like depressions in giant cells and encircled by thorns. The junctional interface exhibits 3 kinds of specialization: (1) puncta adhaerentia, interpreted as simply adhesive; (2) 'active' zones, interpreted as sites of chemical transmission, and (3) 'gap' junctions, interpreted as sites of low electrical resistance between the apposed cells. The physiological implications of this complicated synaptic interface are considered and several possible functions are suggested. Primarily, it is suggested that the operation of such a synaptic interface would be more subtle and delicate than what has been found hitherto. Large terminals and these mixed synapses have not been seen in the cat. Slender terminals are long, relatively straight axons with several varicosities (boutons en passant) along their course, each with 'active' zones. These endings are the least common in the nucleus. The most common are the small endings, which occur on all cell types and are the only ones to appear on the small neurons. No correlation was found between sizes of synaptic vesicles and sizes of the endings as all kinds of terminals contained similar vesicles. Axo-axonal synapses and complex glomeruli are also encountered in this nucleus.