Figure 6.

Effects of single alkaloids on the expression (a) and the acquisition (b) of morphine dependence. Atropine, apoatropine, and 3α-tigloyl-oxitropane were administered i.p. at the dose of 2.2, 1.8, and 1.5 mg/kg, respectively, 30 min before each morphine injection (acquisition) or prior to naloxone injection (expression) (n = 10 animals for each group). The withdrawal symptoms are given as a summary of the frequency of these somatic signs: jumping, rearing, forepaw tremors, and teeth chatter. Significant differences: **P < 0.01, compared to control; ⁺⁺ P < 0.01, compared to morphine group.