Background and purpose:
In this work, a neuroactive peptide from the venom of the neotropical wasp Polybia occidentalis was isolated and its anti‐nociceptive effects were characterized in well‐established pain induction models.
Experimental approach:
Wasp venom was analysed by reverse‐phase HPLC and fractions screened for anti‐nociceptive activity. The structure of the most active fraction was identified by electron‐spray mass spectrometry (ESI‐MS/MS) and it was further assessed in two tests of anti‐nociceptive activity in rats: the hot plate and tail flick tests.
Key Results:
The most active fraction contained a peptide whose structure was Arg‐Pro‐Pro‐Gly‐Phe‐Thr‐Pro‐Phe‐Arg‐OH, which corresponds to that of Thr6‐BK, a bradykinin analogue. This peptide was given by i.c.v. injection to rats. In the tail flick test, Thr6‐BK induced anti‐nociceptive effects, approximately twice as potent as either morphine or bradykinin also given i.c.v. The anti‐nociceptive activity of Thr6‐BK peaked at 30 min after injection and persisted for 2 h, longer than bradykinin. The primary mode of action of Thr6‐BK involved the activation of B2 bradykinin receptors, as anti‐nociceptive effects of Thr6‐BK were antagonized by a selective B2 receptor antagonist.
Conclusions and implications:
Our data indicate that Thr6‐BK acts through B2 bradykinin receptors in the mammalian CNS, evoking antinociceptive behaviour. This activity is remarkably different from that of bradykinin, despite the structural similarities between both peptides. In addition, due to the increased metabolic stability of Thr6‐BK, relative to that of bradykinin, this peptide could provide a novel tool in the investigation of kinin pathways involved with pain.
British Journal of Pharmacology (2007) 151, 860–869; doi: