Effects of Brugmansia arborea Extract and Its Secondary Metabolites on Morphine Tolerance and Dependence in Mice

Abstract

The aim of the present study was to investigate, in vivo, the effect of a Brugmansia arborea extract (BRU), chromatographic fractions (FA and FNA), and isolated alkaloids on the expression and the acquisition of morphine tolerance and dependence. Substances were acutely (for expression) or repeatedly (for acquisition) administered in mice treated with morphine twice daily for 5 or 6 days, in order to make them tolerant or dependent. Morphine tolerance was assessed using the tail-flick test at 1st and 5th days. Morphine dependence was evaluated through the manifestation of withdrawal symptoms induced by naloxone injection at 6th day. Results showed that BRU significantly reduced the expression of morphine tolerance, while it was ineffective to modulate its acquisition. Chromatographic fractions and pure alkaloids failed to reduce morphine tolerance. Conversely BRU, FA, and pure alkaloids administrations significantly attenuated both development and expression of morphine dependence. These data suggest that Brugmansia arborea Lagerh might have human therapeutic potential for treatment of opioid addiction.

Figure 1

Effects of different doses of Brugmansia arborea L. on the expression (a) and the acquisition (b) of tolerance to morphine-induced analgesia. Mice were treated twice daily for 5 days with either saline or 10 mg/kg morphine. BRU (0, 7.5, 15 and 30 mg/kg) was administered 30 min before each morphine injection (acquisition) or prior to the last morphine treatment (expression). Morphine antinociceptive effect (%MPE) was assessed on day 1 and day 5, as indicated. Significant differences: **P < 0.01, compared to control group; ⁺⁺ P < 0.01, compared to related-morphine group on day 1; °°P < 0.01, compared to morphine group on day 5.

Figure 2

Effects of FA and FNA on the expression (a) and the acquisition (b) of tolerance to morphine-induced analgesia. Mice were treated twice daily for 5 days with either saline or 10 mg/kg morphine. FA (5.5 mg/kg) and FNA (24.5 mg/kg) were administered 30 min before each morphine injection (acquisition) or prior to the last morphine treatment (expression). Morphine antinociceptive effect (%MPE) was assessed on day 1 and day 5, as indicated. Significant differences: **P < 0.01, compared to control group; ⁺⁺ P < 0.01, compared to related-morphine group on day 1.

Figure 3

Effects of single alkaloids on the expression (a) and the acquisition (b) of tolerance to morphine-induced analgesia. Mice were treated twice daily for 5 days with either saline or 10 mg/kg morphine. Atropine (2.2 mg/kg), apoatropine (1.8 mg/kg) and 3α-tigloyl-oxitropane (1.5 mg/kg) were administered 30 min before each morphine injection (acquisition) or prior to the last morphine treatment (expression). Morphine antinociceptive effect (%MPE) was assessed on day 1 and day 5, as indicated. Significant differences: **P < 0.01, compared to control group; ⁺⁺ P < 0.01, compared to related-morphine group on day 1.

Figure 4

Effects of different doses of Brugmansia arborea L. on the expression (a) and the acquisition (b) of morphine dependence. Mice were treated twice daily for 5 days with saline or 10 mg/kg morphine treatment. On the sixth day, withdrawal syndromes were precipitated by injection of 5 mg/kg naloxone, 2 h after the last morphine injection. BRU (0, 7.5, 15, and 30 mg/kg) was administered 30 min before each morphine injection (acquisition) or prior to naloxone injection (expression). 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 < 0.05, ⁺⁺ P < 0.01, compared to morphine group.

Figure 5

Effects of FA and FNA on the expression (a) and the acquisition (b) of morphine dependence. FA (5.5 mg/kg) and FNA (24.5 mg/kg) were administered 30 min before each morphine injection twice daily for 5 days (acquisition) or prior to naloxone injection (expression). On the sixth day, withdrawal syndromes were precipitated by injection of 5 mg/kg naloxone, 2 h after the last morphine injection. 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.

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.