Related Experiment Videos
Blockade of spinal pathways decreases pre- and postganglionic discharge differentially
L Qu1, R Sherebrin, L C Weaver
1John P. Robarts Research Institute, University of Western Ontario, London, Canada.
The American Journal of Physiology
|December 1, 1988
Summary
Sympathetic nerve activity to the splanchnic circulation is not solely dependent on supraspinal input. Spinal transection alters, but does not eliminate, preganglionic sympathetic nerve discharge, impacting postganglionic firing patterns.
Area of Science:
- Neuroscience
- Physiology
Background:
- Sympathetic nerve activity typically decreases after spinal cord transection.
- Previous research suggested splanchnic sympathetic outflow is less reliant on supraspinal drive.
- The role of supraspinal input in maintaining sympathetic nerve firing to the splanchnic circulation requires further investigation.
Purpose of the Study:
- To investigate the dependence of sympathetic nerve activity in the splanchnic circulation on supraspinal excitatory drive.
- To determine if sustained sympathetic discharge in the absence of bulbospinal excitation is characteristic of all splanchnic sympathetic nerves.
- To explore the impact of spinal transection on preganglionic and postganglionic sympathetic nerve firing patterns.
Main Methods:
- Spinal cord transection in chloralose-anesthetized cats.
- Recording of sympathetic nerve activity in various pathways including gastric, hepatic, adrenal, lumbar chain, and greater splanchnic nerves.
- Analysis of changes in nerve firing patterns (rhythmic vs. asynchronous) before and after spinal transection.
Main Results:
- Cervical spinal pathway blockade or transection significantly reduced firing in gastric, hepatic, adrenal, and lumbar chain sympathetic nerves.
- Discharge of gastric and hepatic nerves decreased comparably to adrenal and lumbar chain nerves.
- Preganglionic greater splanchnic nerve discharge persisted post-transection, shifting from rhythmic to asynchronous firing.
- Postganglionic gastric, hepatic, and adrenal nerve firing decreased despite sustained, asynchronous preganglionic input.
Conclusions:
- Sustained sympathetic discharge is not a universal characteristic of all splanchnic sympathetic nerves after bulbospinal excitation is removed.
- Preganglionic sympathetic nerve discharge rhythmicity may be crucial for effective synaptic transmission to certain postganglionic neurons.
- The findings challenge the notion of splanchnic sympathetic outflow's complete independence from supraspinal control and highlight the importance of discharge patterns.