Studies on The Response and Morphology of The Cortical Neurons using Double Intracellular labeling

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The present study is aimed to reveal the neuronal morphology using the retrograde or anterograde tract tracing techniques combined with intracellular staining. The experiments were performed on rats, cats and monkeys. Under pentobarbital anesthesia(30mg/kg, i. p.), several fluorescent dyes were injected into certain areas in the cerebral cortex, thalamus and deep cerebellar nuclei. After 1-2 weeks survival, animals were reanesthetized with pentobarbital(same dose)or urethane(2g/kg, i. p.)for acute experiments. Intracellular recordings were done from neurons in the cortex or the thalamus with glass microelectrodes filled with 5% HRP, 2.5% biocytin or 20% Lucifer yellow. The studies on the cat somatosensory cortex using intracellular staining could reveal the mode of the thalamic activation onto the pyramidal neurons and were published in the journal (Exp. Brain Res., 80, '90). The data from rat cortical neurons need more sample records, but preliminary reports have been appeared in the proceedings (Yamamoto et al., '90, '91), which reported the relationship between the firing properties and the morphological features of the cortical neurons. Concerning the cerebello-thalamic projection, we could report the cortical laminar distribution of the thalamic. fibers as well as firing properties of the thalamic VL neurons (Neurosci. Res., 9, '90 ; Exp. Brain Res., 87, '91). Concerning the monkey cerebello-thalamic projection, we tried double tract labeling method to demonstrate the thalamic relays of the cerebello-prefrontal responses, and we could clearly show that the mediodorsal nucleus is one of the thalamic relay nuclei of the cerebello-prefrontal projection, which will be published in the Brain Research in 1992. In the further experiments, we will try to test suitable combination of the fluorescent dyes and intracellular staining dyes.