Transmission of signals through sympathetic ganglia – modulation, integration or simply distribution?
Article first published online: 30 SEP 2003
Acta Physiologica Scandinavica
Volume 177, Issue 3, pages 227–235, March 2003
How to Cite
McLachlan, E. M. (2003), Transmission of signals through sympathetic ganglia – modulation, integration or simply distribution?. Acta Physiologica Scandinavica, 177: 227–235. doi: 10.1046/j.1365-201X.2003.01075.x
- Issue published online: 30 SEP 2003
- Article first published online: 30 SEP 2003
- Received 1 November 2002, accepted 15 December 2002
Aim: On structural grounds, synaptic transmission in sympathetic ganglia is potentially complex with extensive divergence and convergence between preganglionic and postganglionic neurones. In this review, the focus is on what constitutes a functional synapse in sympathetic ganglia and how intracellular recordings have enabled us to identify how the transmission process operates in vivo.
Results: Only one or two suprathreshold or ‘strong’ inputs are involved in activating each postganglionic neurone. The functional significance of the subthreshold or ‘weak’ inputs remains obscure. The strong inputs, and sometimes the weak ones as well, respond in the same way during reflexes. The expansion of ineffective weak connections enables the rapid restoration of functional control after lesions that damage preganglionic neurones. These novel connections may generate erroneous reflex responses after spinal injury. Postganglionic discharge in vivo consists of the summed firing of the strong preganglionic inputs limited, at high preganglionic discharge rates, by the properties of the afterhyperpolarization.
Conclusion: Preganglionic signals are distributed widely through paravertebral ganglia with little modification.