Differential Effects of Morphine Sulphate on Phospholipid Species in The Synaptosomes of The Rat Brain

Studies were carried out to explore the effect of acute and chronic administration of morphine sulphate and drug withdrawal on the concentrations of synaptosomal phospholipid species [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS)] in brain areas of adult male albino rats.
It was found that acute administration of morphine (35 mg/kg body weight) decreased concentrations of synaptosomal PC and PE in cerebellum and increased their levels in striatum. Conversely, PS and PI showed significant increases in cerebellum and significant decreases in striatum.
However, chronic administration of increasing doses (15-75 mg/kg body weight) of the drug decreased the concentrations of synaptosomal PE, PS and PI of striatum and PC in cortex.
Two days after morphine withdrawal the synaptosomal PC, PE, PS and PI showed significant increases in striatum and thalamus-hypothalamus. Conversely, PC and PE concentrations were decreased significantly in synaptosomes of cerebellum after two days of drug withdrawal. Also, after four days of morphine withdrawal, the synaptosomal PC and PE were diminished in cerebellum and increased in cortex.
Overall, the present results suggest that the mechanisms of opioid action are closely associated with changes in the turnover of the brain phospholipid species.