The cardiovascular effects of vasicine, an alkaloid isolated from the leaves of Sida cordifolia L., were evaluated in this work. In non-anaesthetized rats (n=6), vasicine (1, 2.5, 5 and 10 mg/kg; i.v., randomly) induced hypotension associated with an intense bradycardia. Both responses were completely abolished after atropine (2 mg/Kg; i.v.) and attenuated after hexamethonium (20 mg/ Kg; i.v.). In isolated rat mesenteric artery rings, vasicine (0.03, 0.1, 0.3, 1, 3, 10, 30, 100 and 300 µg/mL, cumulatively) induced concentration-dependent relaxation of phenylephrine-induced tone (IC 50 = 3.8±0.9 µg/mL; n = 6). In conclusion, the results show that vasicine produce hypotension and bradycardia which appears to be due to the stimulation of cardiac muscarinic receptors (directly and/or indirectly), and by a decrease of the peripheral resistances.

Macroptilium (Benth.) Urb. is a neotropical legume genus from the subtribe Phaseolinae. The investigated species present a stable chromosome number (2n = 22), but differ in their karyotype formulae, suggesting the presence of chromosome rearrangements. In this work, we comparatively analysed the karyotypes of six species (M. atropurpureum, M. bracteatum, M. erythroloma, M. gracile, M. lathyroides and M. martii) from the two main clades that form the genus. Heterochromatin distribution was investigated with CMA/DAPI staining and fluorescent in situ hybridization (FISH) was used to localise the 5S and 35S ribosomal DNA (rDNA) sites. Single copy BACs (Bacterial Artificial Chromosomes) previously mapped in the related genera Phaseolus L. and Vigna Savi were used to establish chromosome orthologies and to investigate possible rearrangements among species. CMA+/DAPI- bands were observed, mostly associated with rDNA sites. Additional weak, pericentromeric bands were observed on several chromosomes. Although karyotypes were similar, species could be differentiated mainly by the number and position of the 5S and 35S rDNA sites. BAC markers demonstrated conserved synteny of the main rDNA sites on orthologous chromosomes 6 and 10, as previously observed for Phaseolus and Vigna. The karyotypes of the six species could be differentiated, shedding light on its karyotype evolution.

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