engleski

Rostro-caudal differences in the ratio of gabaergic neurons subtypes through the rat neocortex

GABAergic neurons (GABAn) represent 20% of cortical neurons and are a highly diverse group that can be classified using molecular markers: the parvalbumin-expressing neurons account for about 40% of total cortical GABAn population in rodents, around 30% are somatostatin-expressing and 25% are calretinin-expressing neurons. Most of calbindin-expressing GABAn are also somatostatin positive, but significant proportion of somatostatin neurons does not co- express calbindin. However, the level of overlap between the aforementioned interneuron subpopulations is still controversial since some studies have shown additional co- expression between above mentioned markers. In this study we performed systematic assessment of their number and laminar position in frontal, parietal and occipital cortical region to assess proportion of different subclasses and the level of overlap between calretinin neurons and the remaining three subpopulations. A comprehensive qualitative analysis of double- labeled immunofluorescent histological sections showed that there were no major rostro-caudal differences in the number and laminar distribution of calbindin, parvalbumin and somatostatin neurons, while calretinin neurons were more abundant in occipital region. No overlap between calretinin and other major interneuron populations was observed. Parvalbumin, somatostatin and calretinin neurons were evenly distributed within a cortical column, while calbindin neurons were more numerous in upper cortical layers. In conclusion, the laminar distribution of GABAergic interneurons does not differ substantially between rostral and caudal cortical regions, however, calretinin neurons are generally more abundant in caudal than in rostral regions. Data also pointed on the significant difference in proportion and distribution of GABAn subtypes between rodents and primate cerebral cortex.

GABAergic neurons ; interneurons ; rat ; cerebral cortex ; calretinin neurons

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