Non-GABA A-mediated effects of lindane on neurite development and intracellular free calcium ion concentration in cultured rat hippocampal neurons

Abstract

Changes in transmembrane Ca 2+ fluxes and intracellular free Ca 2+ ion concentrations ([Ca 2+] in) regulate many aspects of neurite development in cultured neurons. Lindane has been shown to increase [Ca 2+] in in several cell types. It was therefore hypothesized that lindane exposure would increase [Ca 2+] in and thereby alter neurite development in cultured rat hippocampal neurons. The study reported here showed that lindane (50–100 μ M) increased [Ca 2+] in during short-term exposure (up to 4 hr); in contrast, with long-term exposure (24–48 hr) lindane (1–50 μ m) decreased [Ca 2+] in significantly below control levels. Lindane decreased neurite initiation at high concentrations (25 μ m or above). Lindane increased dendrite number at low concentrations (0.5–1 μ M), but decreased dendrite number at high concentrations (50 μ m or above). Lindane decreased axon and dendrite elongation and branching at 50 μ m. Loading neurons with 1 μm 1,2- bis-( o-aminophenoxy)-ethane- N, N, N′, N′-tetraacetic acid (BAPTA), a calcium chelator that partially ‘clamps’ [Ca 2+] in, eliminated the effects of 50 μ m lindane on [Ca 2+] in in short-term exposures. BAPTA did not significantly reverse the inhibition of neurite initiation or axonal elongation caused by 50 μ m lindane. However, BAPTA partially reversed the inhibition of dendrite elongation and completely reversed the inhibition of axon and dendrite branching caused by 50 μ m lindane. Therefore, some, but not all, of lindane's effects on neurite development may be due to changes in [Ca 2+] in. Picrotoxin, a γ-aminobutyric acid A (GABA A)-associated chloride channel antagonist, had no effect on [Ca 2+] in or any parameters of neurite growth, suggesting that the effects of lindane on neurite development and [Ca 2+] in were not mediated through actions on GABA A-associated chloride channels.