Fig. 2.

In untreated cultures the frequency of mEPSCs is enhanced by phorbol ester, and the frequency of sEPSCs is increased by saline containing 5 or 10 mm Ca²⁺/0.5 mm Mg²⁺, 2.8 or 5 mmSr²⁺/0.5 mm Mg²⁺, or sucrose. Each sweep shows a continuous recording before and after application of 3 μm PDAc (A,phorbol ester), 5 or 10 mmCa²⁺/0.5 mm Mg²⁺, 2.8 or 5 mm Sr²⁺/0.5 mmMg²⁺, or sucrose (100 mm).A, PDAc increased mEPSC frequency in a [Ca²⁺]_o-independent manner in untreated cultures (2.2 Hz before PDAc, 8.1 Hz after PDAc, and 8.5 Hz after subsequent application of Ca²⁺-free/1 mm EGTA-containing saline). B,C, Both 5 or 10 mmCa²⁺/0.5 mm Mg²⁺ and 2.8 or 5 mm Sr²⁺/0.5 mmMg²⁺ increased sEPSC frequency in untreated cultures (1.6 Hz before, and 8.7 and 21.2 Hz after 5 and 10 mmCa²⁺, respectively; 1.8 Hz before, and 2.6 and 7.9 Hz after 2.8 and 5 mm Sr²⁺, respectively). D, Application of 100 mmsucrose enhanced sEPSC frequency in control cultures (1.6 Hz before and 13.2 Hz after sucrose). Data on the increases in mEPSC frequency induced by ionomycin and α-LTx in control cultures are reported inCapogna et al. (1996).