Effects of phencyclidine on contractile forces of isolated rabbit papillary muscles

Phencyclidine (PCP) (0.01-50 mumol.L-1) and its analogue, TCP (0.01-50 mumol.L-1) exhibited positive inotropic effects on electrically stimulated rabbit papillary muscle preparations. Dextrorphan (5 or 10 mumol.L-1) antagonized the actions of PCP in non-competitive manner (pD'2 = 5.25). This demonstrated the involvement of PCP receptors in the positive inotropic effects of PCP. By using high performance liquid chromatography with electrochemical detector (HPLC-ECD), an increase of DOPAC content was found in bath medium after PCP addition. Each of the dopamine receptor antagonists SCH23390, haloperidol and sulpiride (1 mumol.L-1) attenuated the maximal inotropic effects of PCP. These results suggest that PCP induces positive inotropic effects by increasing the release and/or blocking the uptake of dopamine.