Large variability in synaptic XXXX receptor density on interneurons and a comparison with pyramidal-cell spines in the rat hippocampus.

@entity7053 @entity1024 @entity2227 @entity1246 @entity1249 @entity4474 @entity143 @entity140
Pyramidal cells receive input from several types of @entity1246 -releasing interneurons and innervate them reciprocally. Glutamatergic activation of interneurons involves both @entity140 ( @entity140 ) and @entity1024 ( @entity143 ) type @entity2227 receptors expressed in type I synapses, mostly on their dendritic shafts. On average, the synaptic @entity140 receptor content is several times higher on interneurons than in the spines of pyramidal cells. To compare the @entity143 receptor content of synapses, we used a quantitative postembedding immunogold technique on serial electron microscopic sections, and analysed the synapses on interneuron dendrites and pyramidal cell spines in the @entity1249 area. Because all @entity143 receptors contain the obligatory @entity4474 subunit, receptor localisation was carried out using antibodies recognising all splice variants of the @entity4474 subunit. Four populations of synapse were examined: i). on spines of pyramidal cells in stratum (str.) radiatum and str. oriens; ii). on @entity7053 -positive interneuronal dendritic shafts in str. radiatum; iii). on randomly found dendritic shafts in str. oriens and iv). on somatostatin-positive interneuronal dendritic shafts and somata in str. oriens. On average, the size of the synapses on spines was about half of those on interneurons. The four populations of synapse significantly differed in labelling for the @entity4474 subunit. The median density of @entity4474 subunit labelling was highest on pyramidal cell spines. It was lowest in the synapses on @entity7053 -positive dendrites in str. radiatum, where more than half of these synapses were immunonegative. In str. oriens, synapses on interneurons had a high variability of receptor content; some dendrites were similar to those in str. radiatum, including the proximal synapses of somatostatin-positive cells, whereas others had immunoreactivity for the @entity4474 subunit similar to or higher than synapses on pyramidal cell spines. These results show that synaptic @entity143 receptor density differs between pyramidal cells and interneurons. Some interneurons may have a high @entity143 receptor content, whereas others, like some @entity7053 -expressing cells, a particularly low synaptic @entity143 receptor content. Consequently, fast glutamatergic activation of interneurons is expected to show cell type-specific time course and state-dependent dynamics.
