Journal of Neuroscience, Vol 9, 4169-4178, Copyright © 1989 by Society for Neuroscience
Noradrenaline enhances temporal auditory contrast and neuronal timing precision in the cochlear nucleus of the mustached bat
M Kossl and M Vater
Zoologisches Institut, Munchen, Federal Republic of Germany.
In the mustached bat, Pteronotus parnellii, noradrenaline (NA) was applied
iontophoretically to single units in the anteroventral cochlear nucleus. NA
suppressed tonic components of auditory responses and enhanced phasic onset
responses to pure tone stimuli. The enhancement of onset activity was most
pronounced in awake bats and was due to a decrease in the latency jitter of
the first tone-evoked spikes from 0.55 msec in controls to 0.28 msec during
NA application. In addition, NA reduced spontaneous neuronal activity.
Noradrenergic antagonists suppressed phasic onset activity and increased
the latency jitter of onset spikes. Opposite to the effect of NA, the tonic
response component increased during application of the beta-antagonist
propranolol but decreased during injection of the alpha 1-antagonist
corynanthine. Other putative transmitter substances tested, nonselectively
depressed both phasic and tonic response components (GABA, glycine) or
increased both components either similarly or had more pronounced effects
on the tonic response components (ACh, glutamate). Thus, NA specifically
enhances auditory temporal contrast in favor of transients and improves
neuronal timing precision, which may be of relevance for auditory tasks
like passive sound localization, echolocation, and recognition of temporal
patterns.