Localization of the 5-HT1A receptors in the brain of opossum Monodelphis domestica

This paper describes the distribution of 5-HT1A receptors in the brain of opossum Monodelphis domestica. They were visualized by immunohistological staining with an antibody against the amino acid sequence (170-186) of this receptor that was previously successfully used in the rat and monkey. As in Eutherians, high levels of immunostaining were present in the septum, hippocampus, raphe nuclei and some other brain stem nuclei. Neocortex, several thalamic nuclei and hypothalamus showed moderate density of the labeled structures. Moderate levels of 5-HT1A receptors were also observed in the caudate nucleus and putamen, unlike in the rat, in which labeling in these nuclei was almost absent. Another difference with the rat was observed in the neocortex: in the opossum immunostaining was absent in the layer 4 of many cortical areas. In general, distribution and density of this important receptor in the opossum is very similar to that described in the rat and monkey and therefore it follows a general mammalian pattern.