Journal of Neuroscience, Vol 9, 2835-2845, Copyright © 1989 by Society for Neuroscience
Transneuronal regulation of protein synthesis in the brain-stem auditory system of the chick requires synaptic activation
RL Hyson and EW Rubel
Department of Otolaryngology, University of Washington, Seattle 98195.
The cellular mechanisms by which afferents influence their target neurons
were investigated using a slice preparation of the chick brain- stem
auditory system. Each brain slice contained portions of the auditory nerve
and the second-order auditory nucleus, nucleus magnocellularis (NM),
bilaterally. NM neurons on one side of the slice were stimulated either
orthodromically, via activation of the ipsilateral auditory nerve, or
antidromically, via electrical stimulation of their axons. NM neurons on
the other side of the slice were not stimulated and served as a
within-animal control population. Evoked activity was monitored
extracellularly in all preparations. Orthodromic activation of NM neurons
for either 1.5 or 3.5 hr resulted in enhanced protein synthesis by these
neurons. This result is similar to those of previous in vivo experiments
(Steward and Rubel, 1985; Born and Rubel, 1988). When slices were
maintained in a medium having low Ca2+ and high Mg2+ concentrations, both
synaptic transmission from the auditory nerve to NM and also the difference
in protein synthesis between the stimulated and unstimulated sides of the
brain were blocked. Antidromic activation of NM neurons did not enhance
protein synthesis, but rather resulted in reliably less synthesis by the
stimulated cells. Together, these results suggest that activity- dependent
release of some "trophic" substance from the auditory nerve is necessary
for this form of transneuronal regulation. Electrical activity of the
postsynaptic neuron per se is not sufficient for increasing protein
synthesis in these cells.
Previous Article | Next Article
