SELECTIVE SYNAPSE FORMATION DURING SPROUTING AFTER PARTIAL DENERVATION OF THE GUINEA-PIG SUPERIOR CERVICAL GANGLION

J. Physiol., 1981 · DOI: · Published: January 26, 1981

Simple Explanation

This study investigates how nerve cells reconnect after some of their connections are cut. The researchers partially cut the nerves leading to a specific nerve cluster (superior cervical ganglion) in guinea pigs. This caused the remaining intact nerves to sprout new connections. The main finding was that these new connections were not random. The nerves rewired themselves in a specific way, maintaining the original functions of different nerve pathways. This shows that even when nerves need to find new partners, they still manage to connect in a way that preserves the body's normal functions. Researchers found that after a partial nerve cut, the remaining intact nerves didn't just connect to the cells they were already connected to. They also made new connections with other cells. This shows the nervous system has a way of rewiring itself to maintain the original function.

Study Duration

4-16 weeks

Participants

Young adult albino guinea-pigs (200-400 g)

Evidence Level

Not specified

Key Findings

1
Intact preganglionic axons arising from different spinal levels established selective connexions with different classes of ganglion cells during sprouting.
2
After partial denervation, there was a two- to threefold increase in the number of steps in the synaptic response elicited in individual ganglion cells by graded stimulation of the ansa subclavia.
3
The median e.p.s.p. amplitude in neurones thought to be innervated by a single preganglionic axon from the ansa subclavia was greatly increased after sprouting (by about 200%).

Research Summary

The synaptic connexions established by sprouting of intact preganglionic sympathetic axons were examined by intracellular recording in vitro and by observing the sympathetic end organ responses to ventral root stimulation in vivo. These results show that intact preganglionic axons arising from different spinal levels established selective connexions with different classes of ganglion cells during sprouting. In these animals, the end organ responses on the normal and operated side were almost equally strong. However, there was no loss of specificity.

Practical Implications

Understanding Neural Repair

Provides insights into how the nervous system can reorganize itself after injury, which is important for developing therapies for nerve damage.

Specificity in Neural Connections

Highlights the mechanisms that guide the formation of specific connections between nerve cells, contributing to our understanding of neural circuit development and function.

Competitive Interactions in Sprouting

Suggests the presence of competitive interactions between preganglionic axons, implying a complex regulatory process in nerve regeneration and plasticity.

Study Limitations

1
The study focuses on a specific ganglion (superior cervical ganglion) in guinea pigs, which may limit the generalizability of the findings to other species or other parts of the nervous system.
2
The study relies on subjective grading of end-organ responses, which introduces a potential for bias in the assessment of sympathetic effects.
3
The study does not fully elucidate the molecular mechanisms underlying the selective synapse formation observed during sprouting.

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