May 14, 1976

A quantitative comparison of the formation of synapses in the rat superior cervical sympathetic ganglion by its own and by foreign nerve fibres

Brain Research
A OstbergRichard E Zigmond

Abstract

The rat superior cervical sympathetic ganglion (SCG) has about 36,000 neurones in a volume of about 1 cu.mm. There are about 8.8 X 10(6) synapses, and 6000-9000 preganglionic axons. Section of the preganglionic chain causes a loss of 93% of the synapses. In the denervated SCG there are 0.6 X 10(6) remaining ('intrinsic') synapses, and a proportion of the synaptic sites are identifiable as vacated synaptic thickenings (3 X 10(6) per SCG, as compared with 0.5 X 10(6) in the normal intact SCG). After deducting the intrinsic synapses, this indicates that each preganglionic axon forms about 1100 (900-1400) synapses. After freezing the preganglionic chain, subsequent axonal regeneration restores synapse numbers to 85% of normal (7.5 X 10(6) synapses per SCG). After anastomotic repair by suture of the cut ends of the preganglionic chain (a necessary control for the foreign nerve anastomoses), the SCG contains only 60% of the normal complement of synapses (5.2 X 10(6) synapses per SCG). The results of this anastomosis are very variable. However, in individual ganglia the numbers of synapses are directly correlated with the numbers of axons which reach the SCG. After deducting the intrinsic synapses it can be calculated that each axon f...Continue Reading

Mentioned in this Paper

Presynaptic Terminals
Anatomical Anastomosis
Pseudocholinesterase Measurement
Pseudocholinesterase
Hypoglossal Nerve Structure
Autonomic Fibers, Preganglionic
Plant fiber
Nerve Endings
Vagus Nerve Structure
Nerve Regeneration

About this Paper

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