Involment of 5HT1A receptors in the angiogenic-like effects of the Uncaria tomentosa (Willd) DC aqueous extract

Abstract

The aqueous extract of Uncaria tomentosa (EUT) prepared by decoction of the root and stem bark is used in the treatment of several diseases. There is evidence showing the interaction of the extract components with serotonin receptors. Particularly, the 5HT1A receptors strongly involved in the etiology of anxiety and depression disorders. The aim of the present work was to study the involvement of 5HT1A receptors in the anxiogenic-like effect induced by the aqueous extract of Uncaria tomentosa and the influence of estrous cycle. Female albino swiss mice stereotaxically implanted with bilateral stainlesssteel cannuli into lateral ventricles were used. During 20 days, the mice were orally administered with water or EUT. It was used NAN 190 described as 5HT1A autoreceptors partial agonist and 5HT1A postsynaptic receptor antagonist. The animals received<br />a 1 &#956;l intracerebroventricular injection of vehicle or NAN 190 (0.10 &#956;g/&#956;l o 0.25 &#956;g/&#956;l). Five minutes later, the mice were tested in the elevated plus maze. The results obtained showed a significant anxiogenic effect induced by EUT and the higher dose of NAN 190 during the estrous although no differences were found when NAN 190 was administered in EUT treated animals. In the diestrous stage, the low dose of NAN 190 induced an anxiolytic effect and this response was blunted in EUT treated animals. Interestingly, an anxiolytic effect was found with the higher dose of NAN 190 in EUT treated animals. Our findings support a differential action of EUT depending on estrous cycle that could be explained as a desensitization of the 5HT1A autoreceptor induced by estrogen. Since the anxiogenic effect of EUT is observed only under desensitization conditions of 5HT1A autoreceptors, it was concluded that EUT could induce anxiety through an indirect stimulation of the raphe nucleus.