The Organization of Somatostatin-Immunoreactive Cells in the Visual Cortex of the Gerbil

Abstract

Somatostatin (SST) is widely expressed in the brain and plays various, vital roles involved in neuromodulation. The purpose of this study is to characterize the organization of SST neurons in the Mongolian gerbil visual cortex (VC) using immunocytochemistry, quantitative analysis, and confocal microscopy. As a diurnal animal, the Mongolian gerbil provides us with a different perspective to other commonly used nocturnal rodent models. In this study, SST neurons were located in all layers of the VC except in layer I; they were most common in layer V. Most SST neurons were multipolar round/oval or stellate cells. No pyramidal neurons were found. Moreover, 2-color immunofluorescence revealed that only 33.50%, 24.05%, 16.73%, 0%, and 64.57% of SST neurons contained gamma-aminobutyric acid, calbindin-D28K, calretinin, parvalbumin, and calcium/calmodulin-dependent protein kinase II, respectively. In contrast, neuropeptide Y and nitric oxide synthase were abundantly expressed, with 80.07% and 75.41% in SST neurons, respectively. Our immunocytochemical analyses of SST with D1 and D2 dopamine receptors and choline acetyltransferase, α7 and β2 nicotinic acetylcholine receptors suggest that dopaminergic and cholinergic fibers contact some SST neurons. The results showed some distinguishable features of SST neurons and provided some insight into their afferent circuitry in the gerbil VC. These findings may support future studies investigating the role of SST neurons in visual processing.

Immunocytochemical localization of nitric oxide synthase-containing neurons in the visual cortex of the Mongolian gerbil

“…We compared the distributional pattern of NOS-IR neurons in the visual cortex of gerbils with that of other neurochemical markers, i.e., NPY [24] and SST [32]. Notably, we found that the pattern of NOS-IR neurons was similar to that of NPY-IR and SST-IR neurons.…”

“…Somatostatin (SST) exhibits widespread expression throughout the brain and plays diverse significant roles [25][26][27][28][29][30][31]. SST-containing neurons are distributed in layers II-VI of the gerbil visual cortex and include four morphologically different cell types [32]. Gamma-aminobutyric acid (GABA) serves as the primary inhibitory neurotransmitter in the CNS and plays a crucial role in the regulation of the balance between excitation and inhibition among neurons [33][34][35].…”

“…Quantitative analysis. All analytical methods used here were as described previously in detail [24,32,75]. For the quantitative analysis of laminar distribution, NOS-IR neurons were photographed using a Zeiss Axioplan microscope with a 20× Zeiss Plan-Apochromat objective (Carl Zeiss Meditec).…”

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