Low dose effects of PCB on intracellular calcium concentrations in cultured neurons derived from newborn rat ventral medullary surface

Abstract

The central chemoreceptor neurons of the mammals were thought to be distributed over the ventral medullary surface (VMS) that is bathed in cerebrospinal fluid, and are stimulated by excess H⁺ to induce a hyperventilation. Using a voltage-sensitive dye, DiBAC4(3), we found the low dose of PCB (1 microM, Aroclor 1254) effects on the excitability of H⁺-sensitive neurons derived from the newborn rat VMS. In this study, we investigated that the effects of hydroxy PCB (4-OH-2',3,3',4',5'-pentachlorobiphenyl) on intracellular calcium concentrations ([Ca²⁺]_i) in cultured neurons derived from the newborn rat VMS. To monitor [Ca²⁺]_i in cultured neurons, we performed microfluorometric measurements using the fluorescent probe Fluo 3-AM. Expose of cultured neurons to hydroxy PCB dose-dependently increased [Ca²⁺]_i . Cultured neurons exposed to 10, 50 and 100 nM hydroxy PCB showed increases in [Ca²⁺]_i which were at exposure times of 10 min. Higher dose of hydroxy PCB (1 microM) reduced [Ca²⁺]_i in the cultured neurons compared to elevations seen following exposure to 100 nM hydroxy PCB. The increase of [Ca²⁺]_i in the hydroxy PCB solution was blocked with L-type Ca²⁺ channel blocker (10 microM nimodipine). These results suggest that the low dose of hydroxy PCB increases [Ca²⁺]_i in cultured VMS neurons via a mechanism through L-type Ca²⁺ channels. [Jpn J Physiol 54 Suppl:S241 (2004)]