Evaluation of the effects of the herbal product Catuama in inflammatory and neuropathic models of nociception in rats.

Here we evaluated the antinociceptive effects of the herbal drug Catuama in rat inflammatory and neuropathic models of pain, in order to assess some of the mechanisms involved in its actions. Catuama given orally, in both acute and chronic schedules of treatment, consistently inhibited the mechanical allodynia induced by the intraplantar (i.pl.) injection of complete Freund's adjuvant (CFA). The same treatment with Catuama failed to significantly affect CFA-caused thermal hyperalgesia. In addition, Catuama did not significantly modify the mechanical allodynia or hyperalgesia observed following the partial ligation of the sciatic nerve or the diabetic polyneuropathy, respectively. In another series of experiments, Catuama caused a striking reduction of the mechanical allodynia induced by LPS. Oral treatment with Catuama was not, however, effective in altering the production of the pro-inflammatory mediators IL-1beta, TNFalpha, PGE(2) or LTB(4) following i.pl. administration of LPS in the rat paw. Of high interest, the antinociceptive effects of Catuama in the LPS model were reversed significantly by the non-selective dopamine antagonist haloperidol, but not by serotonin methysergide or adrenergic yohimbine receptor antagonists. Our results indicate that the herbal drug Catuama diminishes inflammatory, but not neuropathic, nociceptive responses in rats, by mechanisms involving an interference with dopaminergic pathways. Catuama might represent a potential therapeutic tool for the management of persistent inflammatory pain.