RX 67668 (1-4 mg/kg; i.p.) decreases by half the dose of methacholine necessary to produce red tears, whilst RX 67668 (7-2 mg/kg s.c.) is necessary to reduce the pupil diameter of the mouse to 50% of the control value. RX 67668 (0.3-1.0 mg/kg; i.v.) is effective in reversing tubocurarine-induced muscle blockade [1].