Evidence for a Glutamatergic Pathway from the Guinea Pig Auditory Cortex to the Inferior Colliculus
Version of Record online: 23 NOV 2002
Journal of Neurochemistry
Volume 65, Issue 3, pages 1348–1357, September 1995
How to Cite
Feliciano, M. and Potashner, S. J. (1995), Evidence for a Glutamatergic Pathway from the Guinea Pig Auditory Cortex to the Inferior Colliculus. Journal of Neurochemistry, 65: 1348–1357. doi: 10.1046/j.1471-4159.1995.65031348.x
- Issue online: 23 NOV 2002
- Version of Record online: 23 NOV 2002
- Received January 31, 1995; revised manuscript received March 21, 1995; accepted March 27, 1995.
- Auditory corticocollicular;
- Inferior colliculus;
- Guinea pig
Abstract: We attempt to provide evidence that the projection from the guinea pig auditory cortex (AC) to the inferior colliculus (IC) may contain glutamatergic or GABAergic fibers. Seven days after unilateral AC aspiration, histological studies indicated almost complete AC destruction and preterminal degeneration of fibers and terminal fields in the dorsal cortex (DCIC), external cortex (ECIC), and central nucleus (CNIC) of the IC ipsilateral to the ablated AC. Contralaterally, degeneration appeared in the DCIC. AC ablation depressed the electrically evoked Ca2+-dependent release of d-[3H]aspartate (d-[3H]Asp) in the ipsilateral DCIC, ECIC, and CNIC, and d-[3H]Asp uptake in the CNIC. Together with other evidence that the corticocollicular pathway is excitatory, these findings suggest that this projection may contain glufamatergic and/or aspartatergic (Glu/Asp-ergic) fibers. Glutamic acid decarboxylase immunoreactivity was not apparent in presumed pyramidal cells of layer V of the AC retrogradely labeled with biotinylated dextran injected into the ipsilateral IC. Thus, corticocollicular neurons probably do not synthesize GABA and may not be GABAergic. However, AC ablation depressed [14C]GABA release from the ipsilateral DCIC and ECIC, and [14C]GABA uptake in the DCIC. These findings are consistent with the atrophy or down-regulation of some subcortical neurons that mediate GABAergic transmission in the IC.