Low levels of somatostatin-like immunoreactivity in neocortex resected from presumed seizure foci in epileptic patients.

Overview

The concentration of somatostatin-like immunoreactivity (SS-LI) was determined by radioimmunoassay in neocortical tissue resected from 20 patients with pharmacologically intractable complex partial seizures. Most resections included either the anterior temporal pole neocortex (15 cases) or cingulate gyrus neocortex (3 cases). The concentration of SS-LI was lowest in cortical tissue immediately adjacent to cortical tumors. Preoperative electrical recordings suggested that this tissue was the seizure focus. In vitro recordings showed that this tissue also exhibited abnormal hyperexcitable synaptic responses. Higher levels of SS-LI, similar to normal values previously reported in human cortex, were present in non-focal temporal neocortical tissue (resected from patients in whom the seizure focus was in the ipsilateral hippocampus) in which no hyperexcitable synaptic activity was present in vitro. The functional loss of inhibitory transmitters suggested by the low SS-LI levels might provide a theoretical basis for the hyperexcitability observed in vivo and in vitro.