Increase In Density Of Neurons Research Articles

Chemical sensitivity of neurons in long-isolated slabs of cat cerebral cortex

1. 1. Slabs of suprasylvian cortex were prepared in ten cats by Burns' technique. After 2 months to 2 years, the sensitivity of the isolated neurons to l-glutamate, acetylcholine (ACh) and γ-aminobutyric acid was tested by micro-iontophoresis in acute experiments with or without anesthesia; similar control tests were made in the corresponding area of the other hemisphere. The slabs were then examined histologically and histochemically. 2. 2. Owing to shrinkage of the slabs, and in spite of some loss of large cells of layer V, there was an increase in density of neurons. There was also a marked gliosis. 3. 3. Acetylcholinesterase activity disappeared almost completely from the slabs. 4. 4. There was no spontaneous unit activity in the slabs, and the number of neurons excited by ACh was greatly reduced; the responses were mostly atypical. 5. 5. The isolated neurons showed a reduced sensitivity to glutamate, but the responses had the usual fast time-course. There was no significant change in sensitivity to γ-aminobutyric acid. 6. 6. In four cats under allobarbital anesthesia, areas of cerebral cortex partly isolated for 2–5 weeks showed relatively little change in acetylcholinesterase content, spontaneous unit activity and neuronal sensitivity to glutamate or ACh. 7. 7. It was concluded that these observations gave no indication of any denervation supersensitivity in long-isolated cortex.