FIGURE 5.

Electrical oscillations in isolated DS. (A, Left) We have been able to identify and select isolated DS for electrical manipulation. The patch pipette approached an isolated DS and the seal was obtained by gentle suction of the DS to the pipette (×100). Right. Several isolated DS are observed in the field, but only the DS approached with the patch pipette allowed immunocytochemical labeling with PSD-95 MAGUK, labeled in red and FITC-phalloidin labeled in green. This isolated and others readily labeled were used for the DS-attached approach to study single channel behavior and cytoskeletal manipulations. Spontaneously sealed DS (arrows) allowed “whole-cell” electrical manipulation after patching and breaking in, as shown below. (B) The patch pipette approached an isolated DS and the seal was obtained by gentle suction of the DS to the pipette (×60). (C) Several patterns of electrical oscillations were observed with NMDA in the pipette (n = 12). Electrical oscillations were usually absent in the absence of NMDA (n = 4). (D, Top). Application of Zn²⁺ (1 mM) to the bath blocked the NMDA-activated oscillations (n = 4). Bottom. The electrical oscillations of isolated DS were potentiated by increase in intracellular Ca²⁺ (1 mM Ca²⁺ to bath, n = 7) and decreased by EGTA (5 mM to the bath, n = 4). (E) Fourier spectra of the tracings in d. in the presence of NMDA (black line), and after subsequent addition of Ca²⁺ (Red line) and EGTA (Green line). The downward arrow indicates the fundamental frequency of the oscillations in the presence of Ca²⁺, but not in the control, or EGTA conditions.