Somatosensory evoked potentials in rats with hypocalcemia.

The effects of hypocalcemia on somatosensory evoked potentials (SEPs) were studied in rats. The SEP in awake rats consisted of an unstable, large, negative wave (Nmax) preceded by a small positive one (P1). The P1 appeared to be a subcortical potential and Nmax appeared to represent the function of the cerebral cortex. With the decrease in calcium concentration caused by parathyroidectomy, as well as by administration of EDTA, an augmentation of amplitudes of the Nmax and a reduction in the SEP recovery functions were observed. The latency of P1 was hardly changed. The decrease in the SEP recovery functions possibly reflects a reduction in synaptic efficiency, and the increasing amplitude of the SEP probably reflects the cortical hyperexcitability caused by hypocalcemia.