Figure 4. Lack of I_NaR in nucleated patches from area 35 layer II neurones.

Aa–d illustrates an experiment carried out in a representative nucleated patch; B shows average data from 12 nucleated patches. Aa, microphotograph of the nucleated patch from which the data shown in Aa–d were obtained (patch no. G7307) (calibration bar: 10 μm). Ab, the currents recorded in response to a 20 ms, −10 mV hyperpolarizing voltage square pulse (top) in the whole-cell condition before nucleated-patch isolation (grey trace), and in the nucleated patch (black trace). Note the marked reduction of both capacitive transients and steady-state currents after nucleated-patch isolation. Ac, the currents recorded in the same patch in response to the I_NaT activation protocol (top). Ad, the currents recorded in response to the I_NaR activation protocol (top; only the currents corresponding at the repolarization levels of −35.5, −40.5 and −45.5 mV are shown here). B, average traces obtained from the currents recorded in 12 nucleated patches in response to the I_NaR activation protocol (top). The vertical, dotted lines in Ad and B correspond to the time points at which I_NaR peak would be expected, based on data from intact neurones, at each repolarization level. The horizontal, dotted line in B marks the current level corresponding to the expected I_NaR peak, as determined under the assumption that I_NaR is equally expressed in somatic membranes as in intact whole cells (see Results for details).