Effect of Induction of Spreading Depression by KCL on Caudate Nucleus Firing Pattern: A Single Unit Recording Study

Spreading depression (SD), a phenomenon with ionic and hemodynamic changes in the brain. Studies into this experimental event providesevidence for its involvement in brain pathophysiology. SD plays an important role in some clinical disorders including migraine, cerebrovascular diseases and amnesia. However, further studies are needed to demonstrate the involvement of SD in these clinical disorders. In this study we aim to see what possible changes may occur in firing pattern of caudate nucleus in single cell recording invivo. Materials and Methods: Rats (aged 16–20 weeks) provide from animal house of medical school of Mashhad. Experiments done under ketamine plus xylazine (100 and 20 mg/kg i.p.) anesthesia and application of KCL solution on cerebral surface. For recording EEG, 3 screws, one in frontal and 2 in posterior parieto-occiput area using elab, Science Beam instruments. Iran partodanesh co. apparatus was used. The electroencephalogram was filtered between 1 and 100 Hz and was continuously monitored via an analog monitor scope. For single cell recording from caudate neurons, the electrode lowered through a small burr hole in the skull by Stereotactic coordinates: (AP= 1.2, L= 2.2 and DV= 4). The electrode after isolating active neuron, subdural injection of KCL 0.2 ml at 15 minutes of session performed for each rat via a foramen in skull between EEG electrodes in fronto-parital area and firing rate was recorded for a subsequent period of up to 60 min. Unit records filtered between 300 and 3k Hz. Results: Data shows application of KCL take vigorous effect on firing frequency and some aspect ofpattern like increase frequency and amplitudes. Also some very fast burst firing after minutes of KCL seen. Conclusion: This study shows very direct and fast link between stimulation of cortex and caudate nucleus.