LIMBIC EFFECTS OF REPEATED ELECTROCONVULSIVE STIMULATION ON NEUROPEPTIDE-Y AND SOMATOSTATIN MESSENGER-RNA EXPRESSION IN THE RAT-BRAIN

The aim of this study was to determine the effect of repeated electroc onvulsive stimulation (ECS) on the expression of neuropeptide Y (NPY) and somatostatin (SS) mRNA in the rat brain. For that purpose, quantit ative in situ hybridization histochemistry and RNA blot analysis were used. In the hippocampal formation the prevalence of NPY mRNA positive neurons increased in the hilus of the dentate gyrus and the CA3 while a decrease was seen in layers II-III of the entorhinal cortex. In con trast, SS mRNA was increased in the granule cells of the dentate gyrus and in most neurons of the outer parts of the layer III in the entorh inal cortex with cell bodies of perforant pathway projections to the h ippocampal CA1 region. Both NPY and SS mRNA expressing neurons were in creased in numerical density in the prefrontal cortex with similar amo unts of mRNA in individual NPY positive neurons after the stimulations while SS mRNA levels decreased in hybridization positive neurons. In the striatum the only observed significant effect was an increased pre valence of NPY mRNA positive neurons in the caudal nucleus accumbens. Our results provide an outline of a complex functional anatomy of ECS in the rat brain. This type of investigations contributes to map the n euronal systems involved in the action of ECT used in the treatment of affective and schizophrenic disorders.