SPREADING DEPRESSION IN STRIATUM AND OPTIC LOBES OF CHICKEN

The properties of spreading depression (SD) in cerebral hemispheres and the optic lobe were studied in 30 chickens under allobarbital anesthesia (40 mg/kg). Using multiple capillary electrodes the slow potential change of SD evoked by micro- injection of 25%KCI was recorded from the hyperstriatum, neostriatum, ectostriatum and paleostriatum. Whereas typical slow potential changes (11 mV negativity, 35 sec duration at 50% maximum) were found in the hyperstriatum and neostriatum, SD completely failed to enter the ectostriatum and paleostriatum primitivum, and appeared irregularly and with reduced amplitude in the border region between the above structures. Microinjections of 25% KCI into the paleostriatum augmentatum and optic lobe usually elicited a local negative potential, although spreading slow potential changes of the SD type were also observed exceptionally. It is proposed that the SD susceptibility of different regions of the chicken brain is directly proportional to the surface of somatodendritic membranes and indirectly proportional to the density of myelinated fibers per unit volume of tissue. © 1969.