Electron microscopy of degenerative changes in decentralised rat superior cervical ganglia

Abstract

Decentralised rat superior cervical ganglia and their contralateral control ganglia were excised at intervals of 2hr to 9wk after preganglionic nerve section, fixed in veronal-acetate buffered osmium tetroxide and prepared for electron microscopy. Degenerative changes were observed first at 11hr and were widespread at 24hr. These changes consisted of clumping and/or reduction in number of the synaptic vesicles with their lysis, mitochondrial alterations, separation of the pre- and post-synaptic membrances, breakdown of the axoplasmic and surrounding Schwann cell membranes and digestion of the degenerating material, probably by the Schwann cells (‘Resolution’). Degenerating structures were observed less frequently at 3 days that at 24hr and were scarce by the seventh day after decentralisation. A few synapses at an early stage of degeneration were observed in the seventh day specimens. Most of the few unaltered presynaptic terminals found 7 days after decentralisation contained small (adrenergic-type) granular vesicles, and may have represented adrenergic connections between ganglion cells. The number of these connections may have increased since the 3rd day after decentralisation.