Neural units in the superior cervical ganglion of the guinea‐pig.

Abstract

SUMMARYThe size and arrangement of the set of neurones innervated by individual preganglionic axons (the neural unit) has been investigated in the superior cervical ganglion of the guinea-pig.1. Based on the ratio of preganglionic neurones to ganglion cells, and the average number of axons contacting each ganglion cell, we estimated that individual preganglionic axons innervate on the order of 50-200 superior cervical ganglion cells.2. Of 562 pairs of ganglion cells examined with intracellular recording, forty-seven (84 %) were innervated by one or more common axons.3. Pairs of ganglion cells innervated by the same axon were not necessarily near each other. Although nearby cells were more likely to share innervation than neurones far apart, cells sharing innervation were often found several hundred micrometers apart, and were occasionally separated by the largest dimension of the ganglion (about 1-2 mm).4. The incidence of cell pairs that shared innervation from more than one axon was greater than expected from the frequency of pairs sharing at least one axon.5. Extracellular recordings from small fascicles of the cervical sympathetic trunk showed that preganglionic axons from different segmental levels intermingle extensively en route to the superior cervical ganglion.6. Taken together, these findings support the view that sets of ganglion cells are innervated in common not because of any special topographic relationship within the ganglion, but because they share one or more properties that make them especially attractive to particular preganglionic axons.

Selective control of sympathetic pathways to the kidney, spleen and intestine by the ventrolateral medulla in rats.

“…Convergence of several different preganglionic fibres onto ganglion cells has been reported in the rat (Perri, Sacchi & Casella, 1970) as well as in other species (Wallis & North, 1978;Purves & Hume, 1981). In addition, anatomical studies show that there is considerable branching of individual preganglionic axons to innervate from 50 to 200 ganglion cells (Purves & Wigston, 1983). Since many preganglionic inputs are subthreshold, several inputs must sum to generate an action potential in the ganglion cell (McLachlan, 1974;Skok & Ivanov, 1983).…”

Activation patterns of embryonic chick lumbosacral motoneurones following large spinal cord reversals.

“…7 and 9, and accompanying text). The preganglionic inputs to the ciliary ganglion are segregated among separate ganglionic neurones (Purves & Wigston, 1983;Hume & Purves, 1983) and multiple inputs to a single ganglion neurone are even segregated to different regions of the post-synaptic membrane (Hume & Purves, 1983;Forehand & Purves, 1984). Purves (1983) has proposed that the activation patterns of the preganglionic neurones are instrumental in achieving the input segregation.…”

The Gross Anatomy of the Cranial Cervical Ganglion in the Guinea Pig (Cavia porcellus)

“…Neural units (Purves and Wigston, 1983) and the neurophysiology (De Castro et al, 1995) of the CCG have been studied in the guinea pig. Although the shape, localization and nerve branches of this ganglion have been examined in different species (Getty, 1975a,b;Hedger and Webber, 1976;Mikusek et al, 1994;Cui-Seng et al, 1998;Ç akır, 2001), there are no such data available for the CCG in the guinea pig.…”