Increase in the calcium level following anodal polarization in the rat brain.

The accumulation of calcium ions (Ca) was examined in the rat brain by means of 45Ca autoradiography following the application of a weak anodal direct current to the surface of the sensorimotor cortex. Repetition of the anodal polarization with 3.0 microA for 30 min caused more Ca to accumulate in the cerebral cortex. The degree and extent of accumulation was greater in the hemisphere ipsilateral to the polarization than in the other. Accumulation was also noted in the hippocampus and thalamus. Ca accumulation was detected after 24 h and it remained virtually constant up to 72 h after the last polarization. The results suggest that a long-lasting disturbance of Ca homeostasis is involved in the cortical plastic changes seen following anodal polarization.