Quantitative receptor autoradiography of eight different transmitter-binding sites in the hippocampus of the common marmoset, Callithrix jacchus.

Abstract

The regional and laminar distributions of eight different transmitter-binding sites were measured in the marmoset hippocampus by means of quantitative in vitro receptor autoradiography. Receptors for 5-HT1, L-glutamate, N-methyl-D-aspartate (NMDA) and GABAA were similarly distributed. The highest concentrations of these receptors were found in the pyramidal layer of CA1 and the molecular layer of the dentate gyrus. The 5-HT2 receptors showed the highest concentrations in the oriens layer of CA2. The highest concentrations of muscarinic M1 receptors were seen in the pyramidal layer of CA1. Muscarinic M2 receptors were most densely concentrated in the pyramidal layers of CA1, CA2 and CA3. The noradrenergic alpha 1 receptors were most densely packed in the radiatum-lacunosum-molecular layer of CA2 and the molecular layer of the dentate gyrus. Statistically significant co-distributions of serotoninergic, glutamatergic and GABAergic receptors point to possible interactions between these receptor systems in the same hippocampal regions and layers. Comparisons of marmoset distribution patterns for GABAA, NMDA, L-glutamate and 5-HT1 receptors with those in human hippocampi and those of other primates showed similarities between them. Clear differences in the patterns of alpha 1, M1, M2 and 5-HT2 receptors could be seen between marmoset and human hippocampi, indicating a high degree of species specificity in a presumably "conservative" brain region. More similarities, however, could be found between marmoset and human hippocampi than between those of rat and human brains, especially in relation to 5-HT1 and GABAA receptors and L-glutamate-binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)