Vaucher EJ, Dotigny F (2006) Cell type specificity of the c-Fos immunoreactive neurons of cortical layer IV after patterned visual stimulation. Neuroscience 2006 Abstracts 545.28. Society for Neuroscience, Atlanta, GA.
Summary: The cortical processing of specific visual stimuli may be enhanced or suppressed by neuromodulators, such as acetylcholine or norepinephrine as early as in the primary visual area. We have recently shown using c-Fos immunoreactivity that the specific lesion of basal forebrain cholinergic projections abolished the visually-induced neuronal activity of the layer IV of the primary visual cortex. The present study investigated further which cell types immunoreactive for c-Fos were modulated by the cholinergic afferents. Twenty male Long Evans Rats (275-300g) were anaesthetized with urethane (1.3g/kg). C-Fos immunocytochemistry was used as a single cell resolution marker of functional activity induced by sinusoidal grating in the visual cortex in control condition, specific lesion of the cholinergic fibers using 192-IgG saporin, muscarinic inhibition by scopolamine (1mg/kg) or NMDA receptors inhibition by CPP (10mg/kg). c-Fos/Parvalbumin and c-Fos/rat-brain-pyramidal-cells-marker double immunocytochemistry was performed to determine the localization of the visually-induced c-Fos immunoreactivity within the GABAergic interneurons or pyramidal cells of the layer IV of the rat cortex. The results demonstrated that the c-Fos immunoreactivity evoked by patterned stimulation in layer IV was rarely (less than 5%) co-localized with either parvalbumin or rat-brain-pyramidal-cells-marker. In addition, this functional activity was blocked by a cholinergic deficit but was independent of NMDA receptors transmission, since their inhibition by CPP did not affect the activity-dependent c-Fos immunoreactivity. These results suggest an effect of the patterned visual stimulation and the cholinergic fibers on the excitatory spiny stellate cells rather than the GABAergic or pyramidal cells. It suggests a role of the basal forebrain cholinergic neurons in the modulation of the thalamo-cortical transmission rather than local cortical microcircuitry in the rat visual cortex.
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