Eli Sinnott Silva

Interactions between anandamide-induced anterograde amnesia and post-training memory modulatory systems

Rats were bilaterally implanted with indwelling cannulae in the CA1 region of the dorsal hippocampus. After recovery from surgery, they were trained in a one-trial, step-down inhibitory avoidance task using a 0.5 mA foot shock. The animals received intrahippocampal infusions of either vehicle or anandamide (100 microM, 0.5 microl/side) 30 min before training. Then, either immediately post-training or 3 h later, they received infusions of saline, noradrenaline (0.5 microg/side), SKF 38393 (1.5 microg/side), oxotremorine (0.6 microg/side) or Sp-cAMPs (0.5 microg/side) also in the hippocampus. All animals were tested for retention 24-h post-training. Anandamide produced anterograde amnesia. Immediate, but not delayed, post-training treatment with Sp-cAMPs and noradrenaline reversed this effect. SKF 38393 and oxotremorine had no influence on the amnesia caused by anandamide either when given immediately or 3 h after training. The results suggest that the amnesic effect of anandamide is related to the known noradrenergic regulation of cAMP-dependent protein kinase (PKA) activity previously described in the hippocampus immediately after avoidance training, which is crucial to long-term memory (LTM) formation.

Antinociceptive Effects of the Aqueous Extract of Brugmansia suaveolens Flowers in Mice

The infusion of Brugmansia suaveolens, popularly known as trombeteira or cartucheira, has been used to treat pain in Brazil. The present study was conducted to test for its antinociceptive effects using the abdominal-writhing, formalin, tail-flick, and hot-plate tests in mice. The aqueous extract from B. suaveolens flowers administered intraperitoneally at doses of 100 and 300 mg/kg body weight significantly inhibited acetic acid-induced abdominal constrictions. An increase in hot-plate latency was also observed in animals receiving both doses (100 and 300 mg/kg). In the formalin test, both doses from the aqueous extract inhibited the first (0-5 min) and second phase (20-25 min). Tail-flick assays demonstrated that treatment of animals with plant extract induced attenuation of the response. These results suggest that the aqueous extract from B. suaveolens flowers produced antinociceptive effects, as demonstrated in the experimental models of nociception in mice. This supports popular medicinal uses of this plant as an analgesic.