The over-expression of somatostatin in the gerbil entorhinal cortex induced by seizure

In present study, we investigated the immunohistochemical distribution of s omatostatin (SRIF) in the hippocampal complex of the Mongolian gerbil and i ts association with different sequelae of spontaneous seizures, in an effor t to identify the roles of SRIF in the self-recovery mechanisms in these an imals. In the dentate gyrus and subiculum, SRIF immunoreactive (SRIF+) cell s were similar in both the seizure resistant and the pre-seizure group of s eizure sensitive gerbils. Interestingly, SRIF immunoreactivity was markedly decreased until 12 h postictal. Twenty-four hours after the on-set of seiz ure, the distribution of SRIF immunoreactivity in these regions had slightl y increased. In contrast, in the entorhinal cortex the population of SRIFcells and their density were significantly elevated compared to pre-seizure group 30 min postictal. Twelve hours after the on-set of seizure, however, the population of SRIF+ cells and their density declined, approximately 70 -80% compared to the situation at 30 min postictal. These findings suggest that the enhancement of SRIF expression in gerbil entorhinal cortex may aff ect tissue excitability and have a role in modulating recurrent excitation following seizures. (C) 2000 Elsevier Science B.V. All rights reserved.