Fig. 5.

Effects of a cAMP analog, IBMX, and PKAI on Ca²⁺ currents. Current traces were generated before and after the bath application of cAMP analogs (2.5 mm); both the dibutyryl and the chlorophenylthio analogs of cAMP had similar effects. The difference current traces after the treatment are represented by the dotted lines. The cAMP analogs increased both tLVA (A1) and sHVA (A2) Ca²⁺ currents. Similar results were obtained after the application of IBMX (200 μm), as shown in B1 andB2. After dialysis of cells with PKAI (5 μm), GABA (50 nm) reduced the magnitude of the Ca²⁺ currents as shown inC1 and C2. Traces in A andB were generated from type A cells, and traces inC were from a type B cell. D, Group data showing the effects of both cAMP analogs (n = 7) and IBMX (n = 5) on the sHVA Ca²⁺ current and the effect of GABA on the sHVA Ca²⁺ current in the presence of PKAI (n = 6).