Differential regulation of NMDA receptor-expressing neurons in the rat hippocampus and striatum following bilateral vestibular loss demonstrated using flow cytometry.

There is substantial evidence that loss of vestibular function impairs spatial learning and memory related to hippocampal (HPC) function, as well as increasing evidence that striatal (Str) plasticity is also implicated. Since the N-methyl-d-aspartate (NMDA) subtype of glutamate receptor is considered essential to spatial memory, previous studies have investigated whether the expression of HPC NMDA receptors changes following vestibular loss; however, the results have been contradictory. Here we used a novel flow cytometric method to quantify the number of neurons expressing NMDA receptors in the HPC and Str following bilateral vestibular loss (BVL) in rats. At 7 and 30 days post-op., there was a significant increase in the number of HPC neurons expressing NMDA receptors in the BVL animals, compared to sham controls (P ≤ 0.004 and P ≤ 0.0001, respectively). By contrast, in the Str, at 7 days there was a significant reduction in the number of neurons expressing NMDA receptors in the BVL group (P ≤ 0.05); however, this difference had disappeared by 30 days post-op. These results suggest that BVL causes differential changes in the number of neurons expressing NMDA receptors in the HPC and Str, which may be related to its long-term impairment of spatial memory.

Hemocyte morphology and phagocytic activity in the common cuttlefish (Sepia officinalis).

Little is known about the immune system of cephalopods, in spite of their many highly derived characters within the molluscan clade, including a vertebrate-like high-pressure closed circulatory system. Further the economic importance of cephalopod fisheries, potential for aquaculture, and use as ecotoxicology models demand a thorough understanding of their immune system. In this study, we present a comprehensive characterization of hemocytes in the common cuttlefish Sepia officinalis. Cytological stainings, electron microscopy- and flow cytometry-observations highlight a single granulocyte population with various densities of eosinophilic granules and unstained vesicles. These hemocytes contain acid phosphatase-, lysozyme- and proPO system enzymes, and have high activity in bead phagocytosis assays. Interestingly, bead pre-incubation in plasma results in time-dependent aggregation perhaps resulting from hemocyanin-coating, and decrease in phagocytosis. This study provides the basis for understanding hemocyte-mediated immunity in the common cuttlefish, and essential background for future studies on cephalopod immunity.