Neonatal Proinflammatory Stress and Expression of Neuroinflammation-Associated Genes in the Rat Hippocampus

Biochemistry (Moscow) - Differential effect of the neonatal proinflammatory stress (NPS) on the development of neuroinflammation in the hippocampus and induction of the depressive-like behavior in...     

Mechanisms of heterogeneity of calcium response to kainate and neuronal types in rat cortical primary culture

The dynamics of intracellular Ca²⁺ signal in response to NMDA (N-methyl-D-aspartate, 30 μM) or KA (kainite, 30 μM), its dependence on extracellular Ca²⁺ and the mechanisms of KA-triggered Ca²⁺ entry into neurons have been tested in neurons of rat cortical primary cultures. The level of intracellular free Ca²⁺ concentrations ([Ca²⁺] _i ) was evaluated on Leica SP5 MF confocal microscope using Fluo-3 fluorescent dye, which resolves changes in [Ca²⁺] _i in the micromolar range. The dynamics of [Ca²⁺] _i increase in response to NMDA and KA was different but in both cases the [Ca²⁺] _i increase required the presence of Ca²⁺ in the extracellular solution. The neuronal population was found to be heterogeneous, based on the response to KA applied together with either L-type calcium channel blocker nifedipine (3 μM) or IEM-1460 (3 μM), a blocker of Ca²⁺-permeable AMPAR (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor) lacking GluR2 subunit. Experiments exhibited three types of calcium responses, characteristically belonging to interneurons (expressing Ca²⁺-permeable AMPAR), pyramidal neurons (with AMPAR containing GluR2, making them impermeable to Ca²⁺), and intermediate type of cells expressing both AMPAR types. Thus, we have demonstrated the role of AMPAR and L-type calcium channels in KA-triggered Ca²⁺ entry into neurons. The dynamics of [Ca²⁺] _i during the KA treatment was shown to depend on subunit composition of particular AMPAR subtype expressed in neurons. The data suggest that neuronal types existing in adult cortical tissue are probably presented in primary culture, too.