Interleukin-4 potentiates voltage-activated Ca-currents in Lymnaea neurons.

The effect of interleukin-4 (IL-4) was studied on voltage-gated Ca-current of the neuron RPeD1 of Lymnaea stagnalis L. (Mollusca, Basommatophora), using two-microelectrode voltage-clamp method. It was found that: 1. The neuron RPeD1 possessed a high voltage-activated Ca-current characterized by -40 mV activation threshold and reaching its maximum at +5+5(-)+10 mV. The activation time constant of the current was found to be a monnexponential function of the membrane potential. Currents were almost completely inactivated within 200-300 ms. 2. IL-4 (10-200 U/ml) uniformly and reversibly increased the peak value of Ca-current in a dose- and time-dependent manner (at concentrations 75, 150 and 200 U/ml the potentiation was 5.3 +/- 1.8% (n = 3), 5.5 +/- 1. (n = 3) and 14.6 +/- 7.4% (n = 4), respectively. 3. No changes in the membrane resistance and holding current were observed during IL-4 application. 4. The time constants of activation and inactivation were not affected by IL-4. The maximal conductance as the only kinetic parameter was increased under the influence of IL-4. 5. The affect in modulation of HVA Ca-current caused by IL-4 was additive between the doses of 10-15o U/ml but saturated at concentrations > 200 U/ml. 6. IL-4 antiserum was a potent inhibitor for enhancement of Ca-current by IL-4.