Laminar specific alterations of thalamocortical projections in organotypic cultures following layer 4 disruption in ferret somatosensory cortex
Abstract
The developing neocortex influences the growth of thalamocortical projections. Layer 4 in particular receives the majority of input from the thalamus and is important in instructing thalamic afferents to terminate. Previous in vivo experiments demonstrated that disruption of layer 4 during corticogenesis in ferret somatosensory cortex by application of methylazoxy methanol acetate (MAM) prevents proper termination of thalamic afferents in appropriate cortical regions. To further explore the role of layer 4 in thalamocortical development, we prepared organotypic cocultures consisting of normal gestational day 0 (P0) ferret thalamus paired with normal, embryonic day 33 (E33), or E38 MAM-treated cortex obtained from ferrets at either P0 or P7. Injection of MAM on E33 disrupts layer 4 formation, whereas similar injections on E38 interfere with layer 2 formation. The cocultures grew together for a number of days, then discrete injections of either fluorescent dextrans or 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) were made into the thalamic piece. The labeled thalamic afferents that grew into the cortical slice were analysed and the sites of their terminations quantified after 3, 5, or 7-10 days in cul...Continue Reading
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