Fusion pore analysis. Initial fusion pore conductance (A) and fusion pore opening recorded by patch clamp electrophysiology in (B) untreated and (C) cholesterol-enriched HAS cells. The components of admittance are cell membrane capacitance (C_RBC), AC conductance (G_AC), DC conductance (G_DC), and fusion pore conductance (G_Pore). Fusion pore conductances, G_Pore, were calculated offline from G_AC, G_DC, and C_RBC using software Browse (Ratinov et al., 1998). In HAS cells, the initial fusion pore is small ∼0.2 nS and pore growth is stunted. In cholesterol-enriched HAS cells, fusion pores enlarge, indicating that cholesterol promotes pore expansion (n ≥ 4). The vertical dotted line represents fusion pore opening.