Stimulus-evoked slow potential shifts and changes in [K+]0 of the frog optic tectum.

In 17 frogs (Rana esculenta var ridibunda) immobilised with succinyl choline the optic tectal surface was stimulated by trains of electrical pulses or by a flash to the contralateral eye. Sustained potential shifts (SPSs) and changes in extracellular potassium concentration (delta[K+]0) were simultaneously recorded. In response to electrical stimulation SPSs of maximal amplitudes (1.

Relationships between electrically induced slow negative potentials and changes in extracellular potassium concentrations in cerebral cortex of the cat.

Experiments were carried out on cats under deep nembutal anaesthesia. Local cortical stimulation evoked both a slow negative potential (SNP) and an increase in extracellular potassium ([K+]o) which were maximal in the upper cortical layers. The decline in the K(+)-potential in deeper layers was slower than in the upper ones so that with time [K+]o became equal in upper and deeper layers.