ABSTRACT
Porosomes are the universal secretory machinery in cells where membrane-bound secretory vesicles dock and transiently fuse (kiss-and-run) to release intravesicular contents to the outside of the cell during secretion. Earlier it was shown that in rat neurons 12-17 nm cup-shaped lipoprotein porosomes, possessing a central plug are present at the presynaptic membrane sometimes with 35-50 nm in diameter docked synaptic vesicles. In the current study, neuronal porosome structures following hypokinetic stress were evaluated using electron microscopy. Experiments were carried out to identify and evaluate the porosome structure at the presynaptic membrane in the rat and cat brain in control and experimental
Mzia G. Zhvania,a,b Nadezhda J. Japaridze,b Mariam G. Qsovreli,a Vera G. Okuneva,a,b Arkadi G. Surmava,b and Tamar G. Lordkipanidzea,b aInstitute of Chemical Biology, Ilia State University, 3/5 K. Cholokhashvili Avenue, 0162 Tbilisi, Georgia bDepartment of Neuroanatomy, I. Beriitashvili Center of Experimental BioMedicine, 14, Gotua Street, 0160 Tbilisi, Georgia
animals and to demonstrate the presence of porosomes in the dog brain. The results reveal for the irst time the presence of neuronal porosomes in dog brain and further conirm their existence at the presynaptic membrane in rat and cat brain. Furthermore, the results demonstrate neuronal porosomes to possess a cup-shaped morphology in all the three mammalian species examined, i.e., the rat, cat, and dog. The next series of experiments were designed to evaluate morphological changes in the porosome structure as a consequence of pathological condition-chronic hypokinetic stress. This condition is known to produce structural alterations in the synapses, including the presynaptic regions of limbic region. The depth and diameter of porosome in the central nucleus of amygdale of normal rat and rat subjected to 90 day hypokinetic stress were measured. Morphometric analysis point out the heterogeneity of porosome dimensions that remain unchanged in pathological states. These studies demonstrate for the irst time that despite alterations in the presynaptic terminal structure and synaptic transmission provoked by chronic hypokinetic stress in the limbic region, the gross morphology of porosome is unaffected. These results do not, however, rule out possible changes in the composition of the porosome complex following stress. Furthermore, longer period of stress may elicit changes in the neuronal porosome complex, which remains to be established.
