REGIONAL BRAIN-SEROTONIN RECEPTOR CHANGES IN PORTACAVAL SHUNTED RATS

The pathogenesis of hepatic encephalopathy is unknown, but metabolic p erturbations, including hyperammonaemia and increased brain turnover o f serotonin (5-MT), have been identified. Possible alterations of 5-HT receptors in the brain have been rudimentarily studied. We therefore investigated the 5-HT1A, 5-HT1B and 5-HT2A receptor density in 18-22 d ifferent regions in the brain of portacaval shunted rats by means of r adioligand binding with autoradiographical evaluation. The results rev ealed a decreased 5-HT1A receptor binding in seven serotonergic projec tion areas of the brain, and an increase in tho nucleus accumbans, hyp othalamus and subiculum. No changes in the raphe nuclei were observed. An increased 5-HT1B receptor binding was seen in five brain regions: basal ganglia, olfactorial regions, hippocampus, mid brain and thalamu s. However, decreased binding was seen in three regions of cortical ar eas and hippocampus. The 5-HT2A receptor binding site density was esse ntially unaltered. These findings suggest that perturbations in the ce ntral serotonergic neurotransmission may play a functional role in chr onic hepatic encephalopathy.