[Calcium current effects in the presence and absence of propranolol on cloned neuroblastoma and glioma hybrid cells].

The action of the (-)- and (+)-enantiomers of the beta-adrenoceptor blocking drug propranolol on the inward calcium current (ICa) was studied in single mouse neuroblastoma x rat glioma hybrid cells of clone 108CC5 by suction pipette technique for intracellular perfusion and voltage clamp. ICa was recorded after internal cell perfusion with Tris phosphate buffer and suppression of sodium and potassium currents in Na+-free external solution. Extracellularly applied (-)- and (+)-propranolol (10(-7) to 10(-3) M) inhibited ICa in a similar dose-dependent manner. The IC50 values for both substances were approximately 5 . 10(-6) to 10(-5) M. Two other beta-blockers, alprenolol and talinolol, investigated as reference compounds, also depressed the ICa, but in a significantly higher dose-range of 10(-4) to 10(-3) M. The results provide further evidence that propranolol, besides its known effect on sodium inward current, also possesses marked inhibitory actions on the ICa in mammalian nerve cell membranes at relatively low concentrations.