RESUMO
CONTEXT: Thr6-bradykinin is a peptide found in the venom of social and solitary wasps. This kinin, along with other bradykinin-like peptides, is known to cause irreversible paralysis in insects by presynaptic blockade of cholinergic transmission. However, this activity has never been tested in mammals. OBJECTIVE: As such, the objective of this study was to evaluate the effect of Thr6-bradykinin on the cholinergic system of rats. MATERIALS AND METHODS: The peptide was isolated from the venom of the Neotropical social wasp Polybia occidentalis Olivier (Vespidae). After correct identification and quantification by ESI-MS and MS/MS, the peptide was tested in [14C]-choline uptake using rat cortical synaptosomes. Each uptake assay was accompanied by lactic acid dehydrogenase (LDH) activity measurement to evaluate synaptosome integrity in the presence of six increasing concentrations of BK or Thr6-BK (0.039, 0.156, 0.625, 2.500, 10.000 and 40.000 µM). RESULTS: Data revealed that neither BK nor Thr6-BK at any of the six concentrations tested (from 0.039 to 40.000 µM) affected [14C]-choline uptake in synaptosomes. Moreover, there was no increase in LDH in the supernatants, indicating that BK and Thr6-BK did not disrupt the synaptosomes. DISCUSSION AND CONCLUSION: In contrast to previous reports for the insect central nervous system (CNS), Thr6-BK had no effect on mammalian cholinergic transmission. Nevertheless, this selectivity for the insect CNS, combined with its irreversible mode of action may be relevant to the discovery of new sources of insecticides and could contribute to understanding the role of kinins in the mammalian CNS.