Effect of Cooling on Synaptic Transmission through the Cuneate Nucleus

Authors:
Publisher website
Google Scholar
Abstract
The synaptic transmission through the cuneate nucleus was studied during local cooling of the dorsal column region. Field potentials, recorded from the surface as well as inside the nucleus, were greatly increased during moderate cooling (to 30–25o C) but diminished rapidly if the cuneate temperature fell below about 20o C. The increase was most evident for the afferent fibre volley potentials, but large changes of synaptic potentials (N‐wave) were regularly seen as well. The increase (up to several hundred per cent) was partly rate‐dependent since fast cooling gave larger increases than slower cooling did. In spite of the greatly increased N‐wave, the transmission through the nucleus was always reduced. This was tested in various ways: measurement of the latency and probability of firing of single units, “killed end”–recording from lemniscal fibres as a measure of number of discharging cuneate neurones, and measurement of the size of thalamic and cortical field potential produced by impulses relayed through the cuneate nucleus. The reduced transmission was most likely due to a greatly increased synaptic delay, with slowing of conduction along the terminal branches of the afferent fibres as a contributing factor. On severe cooling blocking of conduction in these branches occurred. During moderate cooling the probability of firing of most relay cells remained strikingly high.

This publication has 11 references indexed in Scilit: