Hippocampus anatomical structure and distribution of agrin proteoglycan and ryanodine receptor expression boost bird food caching behavior

Abstract

Feeding habitats and behavior are connected with various environmental conditions and anatomical structures of the hippocampus, altogether with proteins expression level that may enhance their cognitive memory abilities. The current study investigated the cytoarchitecture anatomical variations, the differences in the hippocampus volume, and the distribution of the proteoglycan agrin and ryanodine receptor protein expression; in the brain hippocampus complex of three avian species (the hooded crow (Corvus cornix, food caching), the cattle egret (Bubulcus ibis, non-food caching), and the rock dove pigeon (Columba livia, food caching). The histological results demonstrated that the anatomical brain structure and cytoarchitecture did not reveal specific characterizing features expect for the hooded crow with large-sized soma. Immunohistochemical staining of hippocampus complex for agrin proteoglycans and ryanodine receptor calcium channels proteins showed a significant increase among the hippocampus of Corvus cornix brain in the medial hippocampus (HCm) and lateral hippocampus (HCl) with value P < 0.001, respectively. The highly expressed agrin may play a major role in constructing the neuronal plasticity and activity of neurons. Moreover, there were significant difference in the concerning hippocampus volume but neurons count did not appeared with for the storing and non-storing behavior. Therefore, the present study revealed a significant difference between storing and non-storing species in the expression of proteoglycan and ryanodine receptor calcium channels proteins. Comprehensively, the hippocampal complex cytoarchitecture altogether with proteoglycan and ryanodine receptor calcium channel proteins are important to birds for fulfilling their cognitive needs such as food caching.