Ketamine inhibits transsarcolemmal calcium entry in guinea pig myocardium: direct evidence by single cell voltage clamp.

To clarify the direct effect of ketamine on calcium entry into myocardium, we directly measured transsarcolemmal calcium entry into single enzymatically dissociated guinea pig myocardial cells by means of the whole cell voltage clamp. Cells were studied in the presence of 0, 10(-5) M, or 10(-4) M ketamine. Peak baseline calcium current was similar in all three groups (911 +/- 92 pA, 954 +/- 66 pA, and 962 +/- 54 pA, respectively). During exposure to ketamine, peak calcium current was unchanged in the no-ketamine control group (886 +/- 74 pA) but decreased in both the 10(-5) M group (723 +/- 38 pA) and the 10(-4) M group (798 +/- 62 pA) (P less than 0.002 vs no-ketamine cells for both groups). We conclude that ketamine has a direct inhibitory effect on transsarcolemmal calcium influx in guinea pig myocardial cells.