Langleys nicotine test

The Langley Nicotine test is used to determine the relay-site of autonomic fibers.

The test is the following: First stimulate the preganglionic fiber and notice the response that appears. By adding a large dose of nicotine, the ganglion (site of relay between pre- and postganglionic fibers) is blocked. Now the preganglionic fiber is restimulated again.

If there is still a response, the fiber does not relay in the ganglion. But if there is no response, the fiber relays ("synapses") in the ganglion.

Langley and his colleague William Dickinson found that in sympathetic ganglia, nicotine acts to selectively block nerve conduction, by causing an interruption between the pre-ganglionic and post-ganglionic nerve fibers. They were able to take this information and develop their test to determine the end points of different nerve fibers.

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