Fig. 5.

Properties of outward currents in type IV neurons. Currents shown in records labeled 3 were obtained by subtraction of control outward currents in records labeled1 from currents recorded after exposure to X-cAMP, 1 mm TEA, or 100 μm 4-AP in records labeled2. A, Block of X-cAMP-sensitive outward currents by 100 μm 4-AP. Top record, cAMP-dependent outward currents in a type IV neuron. Bottom record, In the same neuron as in top recordafter exposure to X-cAMP, outward currents were allowed to recover for 2 min. Then, 100 μm 4-AP was applied via the picospitzer.B, Further evidence for reversibility of X-cAMP modulation of outward currents in type IV neuron. Inset, Extent of inactivation of cAMP-sensitive currents at the end of a 400 msec depolarization to 0 mV in wt neurons. The histogram was built with data from 60 neurons. I, Amplitude of cAMP-sensitive currents at the end of the depolarizing pulse; I peak, peak amplitude of cAMP-sensitive currents at the beginning of the depolarization. The solid line represents the best fitting to two Gaussian components, with peaks at 0.7 and 0.18.C, Outward current block by 1 mm TEA in type IV neuron lacking cAMP-sensitive currents. Top record, Lack of effect of X-cAMP in the type IV neuron. Bottom record, 1 mm TEA blocks outward currents in same type IV neuron as in top record.