Role of ethanolamine phosphate in the hippocampus of rats with acute experimental autoimmune encephalomyelitis

Here, we assessed the effects of acute experimental autoimmune encephalomyelitis (EAE) on the rat hippocampal somatostatinergic system and whether administration of an ethanolamine phosphate salt could prevent the appearance of the clinical signs and the impairment of the somatostatinergic system in this pathological condition. Female Lewis rats were injected in both hindlimb footpads with myelin basic protein from guinea pig brain and complete Freund's adjuvant and were sacrificed when limp tail (grade 1 EAE) or severe hindlimb paralysis (grade 3 EAE) were observed. One group was injected daily with ethanolamine phosphate, starting two days prior to immunization and for 15 days thereafter. The animals were sacrificed 15 days post-immunization. Acute EAE in grade 3 increased anti-myelin basic protein antibodies in rat serum as well as tumor necrosis factor-α and interferon-γ levels in hippocampal extracts. In addition, it decreased the somatostatin receptor density, somatostatin receptor subtype 2 mRNA and protein content, and the inhibitory effect of somatostatin on adenylyl cyclase activity in the hippocampus. The protein levels of the inhibitory G protein subunits αi 1–3, the G protein-coupled receptor kinase isoforms 2, 5 and 6, the phosphorylated cyclic AMP-binding protein and the somatostatin-like immunoreactivity content were unaltered in this brain area. Acute EAE in grade 1 did not modify any of these parameters. Ethanolamine phosphate administration prevented the clinical expression of acute EAE as well as the decrease in the somatostatin receptor density, somatostatin receptor subtype 2 expression and the capacity of somatostatin to inhibit adenylyl cyclase activity at the time-period studied. Furthermore, it blunted the rise in serum anti-myelin basic protein antibodies and hippocampal interferon-γ and tumor necrosis factor-α levels. Altogether, these data suggest that ethanolamine phosphate might provide protection against acute EAE.