ELECTROCONVULSIVE SHOCKS INCREASE THE EXPRESSION OF NEUROPEPTIDE-Y (NPY) MESSENGER-RNA IN THE PIRIFORM CORTEX AND THE DENTATE GYRUS

Repeated electroconvulsive stimulations represent one treatment modali ty for depressive disorders, but the mechanism leading to its effect i s largely unknown. Studies of humans and rats have indicated that neur opeptide Y (NPY) is involved in major depression and anxiety. The purp ose of the present investigation was to detect changes in the expressi on of preproNPY mRNA in the limbic cortex of rats exposed to electroco nvulsive shocks (ECS) daily for 14 days. Twenty-four hours after the l ast ECS, the animals were sacrificed, brain sections were hybridized w ith a synthetic oligonucleotide probe complimentary to rat preproNPY m RNA. Semi-quantitative in situ hybridization histochemistry revealed a n about ten-fold increase of preproNPY mRNA levels over the dentate gy rus and the piriform cortex in animals exposed to ECS compared to sham -treated controls. In the dentate gyrus dipped sections showed that th e increase of gene expression took place in individual neurons in the polymorph layer. In the piriform cortex a moderate increase in the num ber of grains was observed over many individual cells in the pyramidal layer. These data show that the expression of preproNPY mRNA is marke dly increased in specific brains regions after ECS, but whether this i ncrease is a result of the ECS-induced seizures per se, or rather shou ld be regarded as a protective adaptation to changes in neuronal activ ity pattern remains to be established.