[Autoradiographic approach to the developmental study on the binding sites of AVP4-8 in rat hippocampus]

The localization of the 35S-labelled AVP4-8 binding sites in the rat hippocampus was studied by using autoradiographic approach via observing the selective damages of hippocampal neurons by neurotoxins, and the developmental regulation of the hippocampal AVP4-8 receptor by pretreatment with exogenous AVP4-8 was observed. In adult rat hippocampus, the binding sites of AVP4-8 were assembled on the whole hippocampal pyramidal cell layer and granular cell layer of the dentate gyrus. Treatment of colchicine caused parallel disappearances of granular cells and the AVP4-8 binding sites in the gyrus, while treatment of kaininc acid destroyed the CA3-CA4 pyramidal cell layer and abolished the binding sites in this area. The developmental emergences of AVP4-8 binding sites were normally on postnatal day 6 in pyramidal cell layer and postnatal day 7 in the dentate gyrus. However, postnatal daily treatments of exogenous AVP4-8 enhanced the formations of both pyramidal and dentate binding sites, as they appeared rather densely on postnatal day 5. The characterized distribution of AVP4-8 binding sites in the rat hippocampus and the relationship between their developmental enhancements and facilitation of learning behaviors in mature rat by neonatal treatment of exogenous AVP4-8 were discussed.