Changes in Phospholipid Composition of Synaptic Membranes in Frontal Lobes of Cerebral Hemispheres in Cats at Various Stages of Hemorrhagic Shock

Abstract

Phospholipid composition of synaptic membranes in the frontal lobes of cerebral hemispheres was studied in cats with hemorrhagic shock. The compensatory and adaptive mechanisms of regulation of neurotransmission in this region of the brain at the initial stage of hemorrhagic shock are associated with increased degradation of phosphatidylinositol. Accumulation of this phospholipid in synaptic membranes during severe hemorrhagic shock reflects instability of the key neuroregulatory pathway, which is mediated by phosphatidylinositol metabolites. Dysregulation of transmembrane signaling in hemorrhagic shock is related to depletion of phosphatidylcholine and phosphatidylserine in synaptic membranes and accumulation of phosphatidylethanolamine.

Dysregulation of Phospholipid Metabolism in Synaptic Membranes and Their Role in Encephalopathy Forming After a Hemorrhagic Shock

“…This fact is considered as the cause for the increase in the formation of PI 4, 5-bisphosphate, which activate the PC-specific phospholipase D. The metabolic pathway described can cause very rapid and profound changes in the lipid composition of the membranes, accompanied by the formation of micro domains depleted in PI and later on -in PC. At a late stage of HS, the PC level in the synaptic membranes of the frontal part of the brain are normalized [8]. This circumstance may be the result of an increased energy deficit, that prevent the phosphorylation of PI.…”

“…It can directly affect the integrity of the membrane, acting as a detergent. Thus, the initial reduction of PI level in the synaptic membranes of the frontal part of the brain and the medulla oblongata during the initial stage of HS [7,8] may be associated with an increased secretion of neurotransmitters -noradrenaline and acetylcholine, -induced by blood loss and may be reflexion of the existence of the of critical cellular mechanisms which control the modulation of the excitability of neurons and are ways to maintenance of their viability. Moreover, adrenergic and cholinergic hyperactivity of the CNS can be considered as one of the mechanisms of receptors stimulation of EAAs, what is consistent with the existing ideas about the significance in the regulation of these receptors work of adrenergic and cholinergic influences [34,35].…”

“…A fall in the level of PC in the synaptic membranes of the frontal part of the brain occurs in the early stages of the HS [8] and is combined with a decrease in the concentration of PI. In connexion with this are of interest the observations, that during increase of the neurotoxic processes the increase in the hydrolysis of PI is an initial step of Ca2 + -dependent processes, which lead to the damage of the structure of the neurons [4].…”

“…It is controlled by N-methydyltransferase and is related to the synthesis of PC, participating in the formation of the acetylcholine precursorcholine. Increased level of PE, and low content of PC are a distinctive feature of the changes in the PLs spectrum of the synaptic membranes of the frontal part of the brain and medulla oblongata during the development of HS [7,8]. This circumstance does not exclude possibility of slowing down the process of methylation of PE in the nerve endings.…”

“…frontal region of the brain during the early stages of HS is the reduction of phosphatidylinositol (PI) level [7,8]. The metabolism of inositol-containing PLs is considered as the general transduction mechanism for extracellular signals, mediated by various biologically active substances, including neurotransmitters.…”